Well, I could write a piece with a time signature of 4/4 and make it sound like 19/34, but that's not the point of time signatures
The pulse (i.e. the implied time signature, the one *we* hear) is 15/8.
Firstly, if you can't define avant-garde yourself (i.e. don't know what it is), then your piece is almost definitely not avant-garde
"Avant-garde" literally means "front guard" in French, and was used to described the people who were in the very front of the battle field. In the Arts, someone who is an "avant-garde" artist is an artist who pushes the limits further, who "moves music forward", if you want a crude terminology.
Composers such as Stockhausen and Boulez may have been considered avant-garde back in the 50s and 60s, but I doubt many composers would be called "avant-garde" today (even composers such as Carter and Crumb, they are not pushing things any further anymore, they have stayed where they first stepped earlier in their careers - so back then, they were avant-gardists, but not now).
If you want to read a bit more elaborate definitions of "avant-garde", check:
avant-garde - Definitions from Dictionary.com or even the wikipedia article.
Now, how does your piece fit in that description?