Forgive me if this has been discussed before.
I was looking through the ModDB page at some of the renders of Covie ships. Really amazing work. I started saving one of the CAS-Assault Carrier pictures to my Halo folder and noticed a few ships from the Halo comics that I had saved pictures of. I'm not sure if you guys have already seen these or not, but I wanted to bring them to your attention in case you still needed more Covenant ships.
Here we have an agricultural support ship, which is 750 meters long (2460.6 feet). Not sure what this could be used for.
Here's a frigate (not sure on size, though definitely larger than a UNSC destroyer).
Another frigate. This one looks to be winged. 1000 meters (3280 feet)
A super destroyer. This ship is 2000 meters (6600 feet) long.
And here's a supercruiser.
The supercruiser had a length of about 3576 meters, or 11,732 feet (http://halo.wikia.co...nt_supercruiser), so smaller than a CAS-class Assault Carrier. It's mass was about three-times that of a CCS-class Battlecruiser (http://www.halopedia...nt_Supercruiser). It featured 5 energy projectors on the prow and a dorsal turret. Halo Nation also suggests pulse lasers and proton torpedoes, which is logical.
So there are a few nice ships to add to the mod if you guys are looking for more ships.
The other thing I wanted to mention was the CRS-class Light Cruiser model you guys have. It's beautiful, and definitely makes sense in regards to the description in Halo: The Fall of Reach (though I agree with the comments that the wings could be bulked-up). However, according to Halo Nation (http://halo.wikia.co...s_light_cruiser) and Halopedia (http://www.halopedia...s_light_cruiser) the small CCS-class-like ships we see in Halo 4 are actually CRS-class Light Cruisers. Personally I find this kinda lazy and unfortunate, similar to the plot device-class Covenant Plot Device, but I'm not sure how you guys wanted to approach that since Halo 4 is canon. I just wanted to bring that to your guys' attentions.