With the icons of the stratum themes and a preliminary table of what ratios cause the themes to appear.
http://wiki.spiralknights.com/Gate_construction
However, I'm not certain I should have added that table. This is based on a Google Docs spreadsheet I've been using to survey the gates. Unfortunately this was begun as the final preview weekend ran down:
https://spreadsheets.google.com/ccc?key=0AqH-hxlbC7i1dDl0ODBnamN0QzJuOHB...
If I did the wrong thing please let me know and I'll remove the table on the wiki until we get more data when everything opens up again.
You can leave the table on there for now. I may make the note about it being speculative a bit more noticeable, but otherwise I think it's okay for now. I recall that in one of the update notes (http://wiki.spiralknights.com/Release_Notes_2011-03-17) they noted that Wegner will give more information about gate creation later, so hopefully that will add something useful to the mix whenever that happens.