Meanwhile, I'm completely on board with this. Trello is used by a lot of people who make lots of money and want to throw some of it at Fog Creek because they're awesome, but it's also used by a lot of people who make not lots of money (in some cases zero money) and are organizing things like school projects and community service. (For example, I use Trello to organize all my homework, and a club I'm part of at school [with near-zero budget] used Trello to organize a big charity fundraising event.)
This lets the people who want to give Fog Creek money give them money, and get something in return, while letting people who can't afford to give Fog Creek money still use Trello for all the important stuff.
(Also, 250 MB file uploads are a legitimate feature worth paying for. Heck, even pretty backgrounds and stickers are an important feature for a lot of people, just maybe not HN-reading programmers.)