It should work online afaik.
I can bet you it won't, because even the tiniest change in a checksum will cause the game to not allow MP.
For example, two copies of Sins Plus. My version had
one extra file - a map portrait/selection thing I'd made as a quick test. That was enough to cause a fairly significant checksum difference and thus not allow MP.
The new portraits will probably cause a change in the file size and thus alteration of the checksum.
And as rilus said, those backgrounds (at least some of them) are from EVE Online. Not that there's anything
wrong with that per se, but you just won't fool people who have played EVE when they're staring right at a Minmatar Dreadnaught or a Gallente Destroyer from a piece of promo art or a screenshot.