I have been getting alot of my pics framed for me. The pics are mounted on foam core board around 3mm to 5mm thick.then the pics have surrounded by 2 matt boards of varying colour and then framed.
When mounted, the pics can be easily removed from the frame and put into another frame.I try and get them printed at standard sizes to keep costs down for framing.
I have used the same photo store and framer for a few years now and get cracking deals from them for both services.Having this friendship has saved alot of money.
Some of the pics are odd sizes, but again, you get involved in picking the matt board colours and the frame design and colour.Its great watching your pics come to life before your eyes.
After all this people then have the choice of buying it in the frame as displayed and you get good money from them or, if they don't like the frame you just take it out and sell to them without the frame, or again as suggested, if they like the pic but not all the mounting you can offer them a print.
Hope this helps a little.