Custom framing can be expensive. Save yourself tons of money and hang large photos or posters in your own minimalist glass frames.
If you have an odd size print, you can get custom-cut plexiglass. For a 60 by 90cm print, Food52 recommends ordering two 75 by 105cm sheets of plexiglass, which would leave you a 7.5cm border on all sides. Attach the print to one of the sheets with double-sided tape. Then drill holes in the corners of the sheets and use standoff bolts to secure the frame and mount to the wall.
You could also find clear sheets at your local hardware store and either cut them to size or plan your photo prints around the standard sizes.