I would go down to the store buy some decorative rubber mats, cheap as chips, and put over the vent and I would put a few along that seat thing on the front and make a cushion pad for the top. The last pic is what I did with rubber mats, looks like wrought iron lol and have heaps of comments, I actually painted black mats roughly with and off white, waited until it dried and got some steel wool and rubbed a lot off to get that distressed look, it cost me $20, otherwise you could go the dearer way and make up some lattice frames. Good luck

First make sure that the black stuff isn't mold. If it is, you're going to have to do some mitigation. If it's not, then paint everything with a good primer like KIlz. Then paint your baseboards and window casings bright white, paint everything else the same color, whatever color you choose.

Great feedback. Thanks!

Wanted to bump this up..what did you decide as I'm facing the same dilemma?