Poster submissions are welcome.
Posters should be large (A1 size would be reasonable), eye-catching, and interesting. Suggested subjects for posters are pretty much the same as for seminars - anything related to Linux or open source software that is interesting, useful or just plain cool. They will probably be displayed in the area where morning and afternoon tea and coffee will be served; that should help give you an idea of the kind of thing that would be appropriate.
As with the seminar and tutorial material, posters should be supplied in an open format, or at least one that can be created and edited using open source software.
Again as with the seminars, commercial advertising is not appropriate — that needs to go through the sponsorship committee.