Gillette may have one this year. Rock Springs has a tournment on the 19th (pre-registration is going on now), but you have to be a beginner, and it's gravity-fed hoppers only. Otherwise, check around the Cheyenne area, or head a little further South into Colorado to the Blitz paintball field (they usually have something going on around this time of the year).
Otherwise I believe the only other tournament I've heard of in Wyoming, is perhaps Jackson, and I believe they do more scenario style play that direction.
Good luck finding something around here...they're kind of few and far between, but it would be great to get players from other states coming this direction regardless.