Hi Ninja! That art is really cute, but I'm concerned when you say that you're drawing over another image because that sounds a lot like tracing. We don't allow traced art to be sold on Mene because it's not completely "original," thus you'd be making gold for others' work.
When you have the chance, please read through the description of Tracing/Eyeballing/Filtering from the Art Shop FAQ just to make sure that your art meets the guidelines for selling. Thank you & feel free to PM me if you need to. <3
Very cute art! Many artists begin by using bases and progress from them. The safest thing is to make sure that your bases are approved for free use, and that you always link back to them. Once you get proportions down, you can move away. You've got a good start!