Yeah backgrounds are the bane of my existence, I never know what to do when I cant just put some clouds in the back lol. I am kind of an art noob so could you elaborate the contrast thing?
lol, it comes with pracice though. try using interesting patterns and textures if you cant paint one yourself. anything is better than flat colors!
well, for starters, the palette you used is kinda "muddy", try picking clear and more lively colors, without going too wild with saturation. we're looking for harmony, yeah? next thing is to set the contrast according to the lighting. the stronger the light, the higher the contrast, kind of. you can make dramatic and good-looking effects with a little contrast. well, it all depends, if its really dark overall, there wont be much contrast, but that can look good too, if its in harmony with the rest.
so... play around a bit more, add some details, like a little glare in the eye or so. makes it more lively!
and give me a shout if anything needs clarifying...!