Firstly during the massing of the rebel fleet, I noticed no less than 5 ships I couldn't recognise. Here are some screencaps of them, apologies in advance that they are slightly squished sidways:

The top right one looks like it could be a MC ship of some sort, but it looks a different shape than the others. The second looks almost like a Carrack cruiser, which is spooky because the Carrack is an EU invention if I recall correctly. Coming into view on the top right is a ship seen better in the next picture:

Now the ship in the top right is more clear and you can see it has moved position meaning it is not part of the MC ship behind it as I first thought it was. In the top left is what looks like a Corellian corvette but seems to have a modified engine and cockpit section, my thought is it is perhap one of the prototype corvette models they made for ANH re-used as a background filler. However the most interesting to me is the ship in the bottom left, which looks stikingly like a Dreadnought, which again I thought was an EU invention (although I heard it may have been inspred by a ROTJ concept sketch?).

And finally a picture from during the battle of another unkown ship, I put 2 different shots of it there so you could see the "wings" it has on its side, I have no idea what it could be, but from its motion it definately seemed more like a model than a matte painting.
Now it has been over a year since I was able to watch the films on video, so can anyone tell me if these were present in the originals/SEs or if they are new for the DVD?
Also at the end of TESB you can make out the mystery rebel ships much more clearly, I'll take some more shots of them if people want.
Oh and mods, if the images are too big just say and I'll change them to links.