I want to sell a set (only pictures no textures) and I don't remember the artist because I bought this set from long time and I want to know how can sell it and don't be banned for that.

if u bought the set, and did not sold it already yet. means you own the only existing piece of it.

then you are allowed to sell it without any doubts.

but if u already sold it to someone in the past, but dont remember that, you are not allowed to.

No I don't sold it yet but I want to say I don't made it and I don't remember the artist.

Do you have a picture of the set? If you bought the set via a thread on the Market, I might be able to fish out the thread from which you bought it.

If you do not know the previous owner and artist of the set, and you are unable to find out, it is fine if you sell the set without this knowledge. Just state so on your thread.