Save screenshot in memory, not a file

I'm fairly new to unity, I'm getting a good handle on things so far, but the next thing I want to do I'm not really sure where to search for.

What I want to do is take screenshots, many in a level, and then at the end of the level allow the user to select which screenshot to save and which to toss out. What do I need to do to accomplish this goal? I assume once I figure out how to keep them in an array displaying them should be easy...

I know there's a function to save a screenshot to png. But that's not what I'm looking for.

Thanks!