What tipe of bike is it, like what make? I'm not realy into bikes specialy not ones that you can sit up straight on but if it was mine id get some solid alloy rims.. Then i think the frame should either go a bright screaming orange or some similar color, iether that or pitch matt black to make it almost disapear. Then either lotsa chrome or lotsa matt black on the engine and parts or a mix of the 2 might also look nice, and some detail on the seat to create a solid focus point with the tank!
I'll make what i got in mind when i have some time and show you, but I cant even say 4sure if it will look cool as this isnt so much my field.
Its like its obvious the bike isnt a new bike, but then it doesnt seem quite old enough to look like a clasic either, so it falls into that group somewhere in the middle which isnt a nice place to be.. I'd try to make some changes to either make it seem more modern, like you do with a old hot rod, or try to make it look like a vintage one of a kind..