Any self-respecting Skaven army should have a nice big swarm of rats, and that's what I have:
I really like swarms in general - I have a soft spot for things like snotlings, jungle swarms, scarab swarms, ripper swarms and so on. They're usually really good as a flank guard because they never break, take a long time to kill, and can be flung into things like Chosen Knights of Khorne as redirectors or even just tarpits. This is why I almost always take five bases if I can, and this army's no exception.
As they're second hand, they haven't been built the way I would have done (they're very same-y, with one large rat on the front right, and a funny rat-with-knife-and-cloak in the middle rear) but they are mostly complete. I drybrushed some of them grey and some of them black, repainted all the cloaks from blue to undyed cloth colours, and then hit them all with Agrax Earthshade. The next step will be to highlight the cloaks and then paint all the tails, paws, and bony protrusions (and poxes). I should be able to get all that done tomorrow.