You only need to include models that are used in your map. You can pack them into your bsp using pakrat, which means no additional files are required to be downloaded into the model/materials directory's etc.
If you don't use them, don't include them.
If you do, pakrat them.
The swamp theme is not an official pack for this contest, it is just a pack made by this community that is free game for this contest.
edit:
What should we do when we finish the map? Post the .bsp or just a bunch of screenshots?
An upoad thread will be made closer to the deadline. Paste a link to your maps upload url (tf2maps or dropbox) there when the time comes.
Usually we don't allow screen shots so that players are not tempted to judge the maps by the limited screen shots provided with the bsp, so that people actually play the map and get the full experience (soundscapes etc).