Hello Thomas,
Just a few questions for you in return:
How long have you been playing piano? What would you consider to be the "hardest" piece you have played/mastered? Which chapter do you plan on entering in the CMC (in other words, what city do you live in)? And finally, have you played concertos before? If you have, which ones?
My advice to you:
You should familiarize yourself with the repertoire requirements for the Age 17 category. Be very sure about what pieces you are playing to use. Also, do not use pieces that are largely overplayed; for example, the Chopin Nocturne and Revolutionary Etude that you are currently playing. Also, Pathétique would not be such a good option since it will be played in lower age categories, I have heard it this year in the 13 and 14 y/o age groups. Once you have a basic out line of your repertoire, feel free to put it on this forum so that some senior members and I could give you some more suggestions.
In terms of your choice of concerto:
You should play something that will fill up ALL or most of the given time which I believe is 25 minutes. Some of my suggestions for the concerto would be the:
-Ginastera Concerto No. 2
-Rubinstein Concerto No. 4
-Rachmaninoff
-Prokofiev
-Bartok
-Tchaikovsky No. 1
Mendelssohn no.1, liszt no.1.
I feel like the Mendelssohn could also be an effective concerto to perform. The Liszt as well though it may be a little overplayed and does not fill up the time limit too well.
Sorry about this very long post but hope this helps. If you have any other questions, you can reply and I will try me best to check this topic every day or so.
--Superman1980--
Ps. I'm assuming you will have the help of your teacher also, right? If so, would you mind telling me who he/she is via PM, of course

?