I did gnomenriegen for my college auditions and they seemed to like it. I think it is a great piece to play, it's hard, but not too hard, and fun. I've never met anyone who played it at an audition so I don't suppose it's that common.
I think the Medner suggestion is great, have you looked at op20 no1? Thats an incredible piece if music.
I know a lot of people tend to have at least one big piece, and I think Ondine is a great one to play, or even a chopin Ballade, although they hear them a lot.
Don't ever be put off by people playing stuff like Islamey and feux follets. They don't just go for technique at colleges. If they play them well, be scared, but I highly doubt it, they've probably spent all there life learning islamey, and have a totally rubbish programme after that. Academy loves that sort of stuff though, a teacher from there once told me... Academy students all play fast and loud, and nothing else. And they favour foriegn students big style for money. That was an actual teacher at academy that told me that.
Trinity love new music, at my audition there thats all they talked about in the interview "Do you like contempory music?". They made me play for literally 5 mins. I played about 2 pages of Chopin scherzo 3, and then gnomenrigen, and they stopped me.
Are you going to apply for Guildhall? Thats a great place as well.