Sometimes the best solution to creative block, in my opinion, is to just straight up walk away. There are times when people will contact me to hire me for commission and in the middle of their spiel, even before telling me all of the things they'd like and all of the important details to be included, I've got it. They haven't even finished telling me what they want and I already know what I'm going to do. And how I'm going to do it. That feeling of knowingness is almost always followed by pure excitement, and it is pure friggin joy. Other times, they will go on and on until they've relayed all of their awesome ideas and still no vision has popped into my head.
The most effective way, that I have come up with, to handle these moments of utter blankness -is to simply walk away. Not forever, of course. No vision now definitely does not mean no vision later. My solution is to leave it behind and let it go until I'm ready to approach the problem again, this time hopefully, with a clean palette and new perspective. Waiting it out, re-approaching and then diving back in can usually breath new life into a dead idea. Instead of just putting a band-aid on it by doing some basic painting that doesn't mean a whole lot to me, I let it fester.