You hear time and time again that you should never make your art first, build gameplay first. I have been starting games for years and slowly grinding to a stop because I start working on the art and never get back to designing my game idea. When I came over to Construct2 from Torque2s/3d, Unity, Stencyl, Game Maker, and even some CraftStudio I decided to make a learning game and only use art I made in the internal sprite editor. It was pretty fun and I stuck to it and finally released a pretty stable 100 level side scrolling space shooter using just Construct2 editor art. It was so much easier when I didn't worry about my art and just focused on gameplay.. the art turned out pretty cool and game is actually fun I hear.
My advise would be to do the same, make generic art using ediitor even if its just stick figures. If your gameplay is a super fun hit you can always find or hire an artist.
My game is on the arcade and link is in my Sig below if anyone wants to see my uber cheesy editor art.