I noticed while trying to set tags for an event that there are a limited amount of tag and combinations available, and you can’t see what the available selections are.
Is it possible to select multiple tags from a drop-down list and make suggestions for new tags?
I have a FREE and powerful MP3 tagging program called MP3TAG with an extensive list that I am going to try to pull and submit.
You are mistaken; there are no limitations whatsoever to tags you set to your events. You can create whatever tags you like.
We probably start promoting the most popular at some point (obvious ones like “house”, “trance” etc) but we’re not there yet 
What we are doing currently is looking help for testing out Genre TOP-40 Lists and news related to tags/genres – all help is welcome!
Are the tags limited to single “words”. That may be my issue.
Yes, tags can be anything you like, but whitespace nor other special characters (other than a-z) are not allowed. Ie. use only “single words” separated by a comma.