Are you allowed to use your own drawings for entries like those about aliens?

I noticed that here most of the alien pictures used are mostly spore or other creator-type programs to make alien layouts. As for me, I make mediocre drawing art using typical art though I find it the most easier to create something on the most primitive art programs due to starting out with older computers.

I got confused by that copyright thing, since it was mentioned seriously, but there weren't additional mentions about this subject.