The key cards in your display are not particularly attractive on the whole, with most being very common.
Unless the display has some personal meaning to you .... such as from hotels that you have actually stayed at ... I doubt that most collectors I know would be interested in purchasing it at $75 ... too many generic keys. (I'm guessing that you are an airlines employee or in the travel industry)?

My suggestions for your next attempt ...; Utilize keys in a more pleasing symetrical pattern, such as all horizontal or all vertical format, or alternating rows of vertical vs. horizontal ... or use vertical keys around the four outter sides with horizontal keys in the middle. Use keys that have specific hotel names (preferably from casino hotels). Use keys that have more colorful designs, or consider using a theme, such as keys from a specific geographical area, or keys that depict performers or some other common subject; like keys that have pictures of the actual hotel building.

Just a few of my candid comments. I'm sure that others may have additional constructive suggestions.

Oh, a futher suggesting regarding mounting. Staples, Office Max, Office Depot has a tackless mounting product that looks and feels similar to silly putty that is used for hanging pictures on walls without nails. It is easily removable to make changes and does not leave any residue. You would only need a tiny speck on the back of each card in your frame.