hey,
i play toribash for a long time and know that there are really good artists in this forum.. my question is: is it possible to request art stuff that is not related to toribash ( so no texture set or signature) ?

I don't see why not, although it may be harder to find an artist on this forum for it.

I've seen many non-toribash related requests, one was a facebook profile

Of course it is, just open a thread on the Market with your request, following the rules, of course (and enough TC).