If you're looking for free software then your best bet is GIMP. I hear the interface is pretty dense but it's been around long enough that there's bound to be a YouTube tutorial for whatever you want to do.

Gimp has shapes and layers which may be perfect but if it's really more about geometric design than about pixels, then Inkscape is probably more suited. (Even) more impenetrable interface for first time users, though.

Cool thank you!