yeah you can do just about anything as long as you have a decent knowledge in electrical currents mainly when dealing with things like LED's. The mouse is run off the +5v rail and so there IS enough power in the mouse to power LED's, possibly not those SUPER BRIGHTS! or something along those lines, but it should be able to light up 4 as long as you make the circuit correctly.
has a lot of useful information for modding just about everything in your computer.
Creating different pictures with colors? I don't know exactly what you mean there, but if you wanted LED's to be timed differently well that requires a lot more than just giving juice to them. You'd have to actually get a little micro chip from radio shak that alters the timings of those things.