If you're sure you want to you can but as long as you're positive you want to. I just know if it'd taken someone to do art for me I wouldn't even want the art let alone to tip them. So if you're sure you want to you can.
I'm still working on it. I messed up somewhere along the way and now I have to undo a lot of what I did on it to fix it. I don't want you to tip since it's taken me so long to do it.