Not really, no. Sonnets and parodies/imitations of famous poems are what I get most often, but I accept any other format of poem as well. I guess the only limitations are that they should be related to Homestuck, and should be, y’know, poems. Oh, and they should probably be longer than a single haiku, but shorter than a thousand-line epic. Other than that, go nuts.
I try to give the authors as much control over their submissions as possible, so if you have any requests about how I should credit you, what format you’d like it in, if you want a little note at the beginning/end, or anything like that, just let me know. If I think a poem would benefit from it, I’ll sometimes make an image to go with it, but if I do, I’ll run it by the poet for approval before I publish it. I’ll try to fix any typos or punctuation/formatting errors, but even in those cases, I’ll ask the poet for permission before editing a single character. (I’m still bearing a decade-old grudge at the Neopets poetry contest for changing “prophesy” to “prophesize” in one of my poems. It threw my rhyme off, and “prophesize” isn’t even a real word. Freakin’ Neopets.)
One final word about submissions: I’ve got a pretty sizable backlog of them to go through at the moment, and I want to post them in the order they were received. Which means that anything someone submits now probably won’t be show up on the blog for at least a few weeks. I’m familiar with the “did Tumblr eat my ask?” paranoia, though, so don’t hesitate to send me a “did you get it?” message if you’re worried.