Just that really. After 20+ years of Indie/rock I'm reverting to the music I had the privilege of being introduced to as a child. The Brahms thread below interested me so may try a bit of that...so what else would I like?
There's nobody quite like Sibelius, but Nielsen is a contemporary and an equally unique voice. There are few Scandinavian composers of a similar stature, but Nils Gade and Johan Svendsen might be worth a listen.
After Tchaikovsky, there's Borodin, Rimsky-Korsakoff, Glazunov (going through a bit of a revival at the moment), and on to Shostakovich, Rachmaninov, Prokofiev, Kalinnikov and Myaskovsky. Venturing into nearby lands, Dvořák and Smetana, and perhaps on to Suk, Janáček, and maybe even Martinů.
From Elgar, you could try Parry or Moeran or Delius.
Maybe venture into Germany and Austria with Mendelssohn, Schubert, Schumann, Strauss (Richard), Mahler and Bruckner.
Or into France with Berlioz, Debussy, Fauré and Ravel. Maybe even some Poulenc.
Or even to Italy and Respighi, or Spain and Albéniz.
If you get through that, I've got more suggestions...