Are there any inherent shortcomings in this schema?
Unfortunately, it's very difficult to just cast one's eye over a schema and say, "Yep that's great" or "Yes, that's going to work".

Schema and system design is an iterative process - you start with a few ideas, implement them and test to see how it's working. Then you rejig the bits that aren't working and see - now the rejigging will (in all likelihood) break some bits that were working previously and that you hadn't changed - so you tweak again, and hopefully you asymptotically approach (nirvana...) a decent working app.

I can only advise you to 


visit databaseanswers.org - check out databaseanswers - there's lots of links related to tickets and events, and
check out your search engine of choice for "open source reservation systems" (or similar) and download some systems and check out their schemas.


Sorry not to be able to be of more help, but it's analagous to asking "I'm thinking about writing a book, here are the chapter titles, will it be good?".

Start out your system and if you have more specific questions, come back here and ask them - p.s. welcome to the forum.