I used brass angle rods, glass fiber plates and screws for the case. A raspberry pi 2, this time with its own camera module. A TFT screen, the thermal printer, and a lipo battery. More details here:
During a party, the 3.6Ah lipo was able to keep running the raspberry pi for around 6h, plus around 100 prints !
I found a large aperture CCTV lens to get maximum sensibility. The counter part is it need to be manually focused.
It is worth to mention few facts about the paper. Thermal paper is very cheap and could be easily found without BPA, but it is sensible to sunlight and heat. Exposed to sun, the prints will fade with time.