I had a show two weekends ago and had no budget for framing. I decided on using very small and powerful rare earth magnets, one on each corner, with metal thumbtacks on the wall beneath the print. The prints were 26x30 inches and held quite well. I did need to flaten the prints onto the wall by applying pressure to them with a cotton gloved hand each morning of the 2 day event. The magnets cost me $100 with shipping, and the gallery did find the budget to reinburse me. I ended up paying for the thumtacks, about $2.50 It actually looked quite good.
This is a really interesting idea.
No idea what's going to happen next, but I'm hoping it involves being wrist deep in chemicals come the weekend.