For me, feelings are a great source of inspiration. Actually, feelings are probably the thing that encourage you to design, illustrate, paint or whatever. Any feeling is a good way to get your brain juices pumped and running, and this guy, Jirat, uses lots of rage in his super colorful illustrations.
I'm not saying Jirat is an angry guy, but his illustrations definetely make us think about punching faces or kicking asses...now add some super crazy colors, and you get yourself an awesome set of illustrations! And where does he get inspired? He answered that in his portfolio: