I feel like I know what you're trying to get across, but I feel like it can't be possible. I have a few questions/statements
A. Are you saying that we use our own points as the currency? If it is not points, then what is the currency?
B. If there is an item on the 'pointshop' that costs 622,847 points (Which is my current point total as I am writing this), what will happen once all my points are depleted? All those memes that got hundreds of upvotes, thus bringing along thousands of points with them, all gone, and are now useless. Will my previous icons disappear now that I'm at 0 points?
C. Going off of what Ponyration said, it could be used as a way of cheating as users make custom colors the exact same colors as the ones that are earned when you subscribe to Imgflip Pro (Green and Purple). This can be used as a major loophole.
D. This also takes Imgflip away from being an image hosting website. Sure custom icons are cool and all, but you only see icons on mainly comments and the user's profile page.