Great... perhaps instead of the sharp square edges, you could put the blueprint on a sheet of paper with curled up edges? Something that gives it a nicer 'edge'?
That's a good idea and would highlight the blueprint character even more. But making the edges more complex means stealing some space from the inner part. Shouldn't be a problem for 512x512 and 64x64 but for the smaller 32x32 and 16x16 icons (which will be relevant for the icons used on the BitcoinQt fork that will be seen a lot by users) it might mean the "P" and the measurement lines become hard to recognize.
Anyway, I will play around with it some more tomorrow and see what I can do. Maybe only the bigger versions could get the nicer edges and the smaller ones could be left as is.