Hey there!
I'm happy to offer feedback! I took a look at your designs tonight!
Quick Note:
Your very fond of stretching parts, this can really hurt the textures, so I think these designs will only work well with specific textures. I would make note of that, and if you ever get into modding appearances, note you can control texture sizing when you do.
Duruyan: Love this guy, for a tiny hull, he is very ornate. I like the spinning center, and hope to see more of that in the other designs. Shipsets need common themes from ship to ship, and in general, I think it helps if power sources, lighting, and engines are fairly consistent. My only problem with this ship is the head, you used Relic 19, and stretched it well beyond what I think works, as a result, it doesn't blend well with the other parts. Try using more parts to get the same shape. For example, you are already using Thalan 55 a bunch. If you were to rotate two of them you could make the same shape for the head of the craft, you'd just have to fill the center of the disk with something, but the parts would mesh well, and you'd get a more detailed looking model anyways.
Cyven: WOW. Neato effect using the prometheon! But I worry if I'll see this again on other designs (I'm writing as I'm looking) the consistency of the set is breaking down a little. This effect looks like water running over a surface, its really super creative. You could make that the central component of an entire shipset.
I like that we are seeing more detail here. Thalan 65, is fairly flat but curved and you've attached some pieces. But your allowing the engine colors to show through, but they are partially covered. I would endeavor to cover these lights, they aren't being purposefully used and detract from the model. Your use of tiny blue lights all over is great btw. However, you didn't sink them deep enough, so I can see the little rim with yellow on each one. Now that isn't bad, but your models are light on details, especially small details, so I would either A) add more small details or 
sink these lights a bit. Your also using a Krynn light panel, but its bigger than the object surface its laying on and I can see it extend off an edge. I would make sure these light panels are flush, and sized so that they always have a good thickness beneath them. Otherwise, where is the machinery that powers the lights eh?
I absolutely love the outline of this design. It has a flourish, and reminds me of manta rays and fancy fish, or exotic bird perhaps. BUT, the parts are so incredibly thin, that I have to ask... where is the crew? I have a lot of trouble designing ships with this sort of aesthetic, because I'm a little bit of a realist. I would really love to see this concept grown into a Medium Hull and thickened up a bit. The same profile would be great, with a big open maw in the front, as a large or huge hull carrier.
The crystals... I can take it or leave it.
Illiuyi: I like this guy. He has a bit more heft than the other designs and I think he works well as a small hull. I'd like to see the spinning orb of the Duruyan, applied to this guy. You already have a circular indentation on the bottom of the craft where this could be done. The lights on the sides of the tail fins... well, they are too thick and stand up. The profiles of these ships is very elegant and smooth, to have a square block sticking straight out of them is jarring.
Meleaia: I like this ship overall, but it strikes me as a small hull not a medium. The Cyven and this ship could easily swap. You use prometheon again, but in a uncreative way compared to the Cyven. Very nice use of Thalan 86 as both a structure point, light, and engine!
Nuraya: Well... okay... this little guy strikes me as a sensor ship, perhaps meant to be a surveyor? But, he uses many less parts than the other ships, and is much simpler, and he uses Thalan 86 for the head, but stretched beyond good taste. I would make his head piece unstretched, and convert this hull into a tiny probe. The Meleaia works much better as a surveyor, I just feel like it needs a bit more bulk, maybe in its head piece.
I suspect these two ships were made first?
Yllanith: WOAH! What a crystal surprise this guy is! Certainly feels like a large and in charge ship! We are back to a spinning orb from the Duruyan (hurray consistency!), but its stretched, and looks like its spinning directly into a solid surface (because it is). When you have components like this, you need to apply some "window dressing", so you can't see it merge so easily into the rest of the ship, tightening the circlet pieces around it should help. Also I despise spheres that have been stretched like this, and rotating really hurts it. I would destretch that.
This is also the first ships where I thought "Okay, like more than 2-10 people are on this thing. This one strikes a good balance of heft.
The Sylph... wow... that is quite the device inside it.
Alright, running out of time, so I have to conclude, I did look at the other 3-4 ships.
1) You are doing some cool things here. Each ship seems to try something new. Some of it works, some of it doesn't (the huge hull, with the rings attached to crystals at the end... Nope. Doesn't work IMO).
2) Your capable of super details and some interesting animations, the Slyph proves that.
3) You have a really good eye for the profiles of a ship, these all have really interesting shapes and profiles.
BUT?
The shipset totally lacks consistency. I think you learned a lot from building these, and now its time to reimagine the set again, but this time, pick some gimmicks/ideas/themes and stick to it. There are too many fun ideas in these ships and it breaks them as a set. You have:
Crystals. Spinning Thalan Tech Orbs. Spinning Rings (on the Huge and a few others). Krynn Square Lights, Lots of Round Lights. Prometheon weirdness.
That is just too much in my opinion. I would seriously consider dumping the crystals, they sharply contrast and don't work great with the rounded parts you have selected. I would be most interested to see the Cyven's effect applied to this set, as its really unique, but otherwise Spinning Thalan Tech Orbs.
And in general? I think you should apply the design philosophy of the Slyph to the whole set. Each ship, could have a very distinct "head piece" where crew live/function, followed by a skeletal spinal column of details, tubes, etc. like the Slyph, all of which has wings and ribs of curved thalan parts. It would make the whole set come alive, and yet remind me of death, as it would like bird and fish skeletons on display in a museum.
I think if you really focused (and this is most important), and added a dash of practicality to these designs (seriously. Aliens gotta live on these remember), and also, put some thought into designing weapons for these, that this would make a really superb set, in a style that I really struggle with!
I hope the feedback is useful!
