FYI, you can get up to 250 now -- it's 100 icons with a paid account and 250 icons with a premium paid account!

We're looking at whether or not we can raise those limits (stay tuned, as we work out spreadsheets and mutter mystical incantations, etc), but the way we're conceptualizing icon add-on packs, hopefully you'll be able to buy them in batches up to however many you want. I'm not sure what will wind up being technically possible (the account type structures are kind of hard-baked into the site in a lot of places and I'm not sure if it's going to be possible to allow arbitrary number of icons without, like, recoding half of everything), but believe me, we definitely know that people want to be able to buy more icons. ;)