Echochrome producer Kumi Yuasa has promised that user-created puzzles will be available to download for free on a regular basis.
The developers will hand-pick each batch, and they will be playable for as long as it takes the team to select and release a subsequent compilation.
To have your creation included, simply select "Canvas" from the main menu and tinker until you can play and complete your puzzle.
Once finished, pop to the portfolio menu and either "send" it to a friend or "upload" it to the developers. In the PSP version you can only "send" your levels Ad Hoc to friends.
Echochrome, sadly, is yet to be released in Europe, although the US has had it since 1st May and Japan since 19th March.