impossible

Looking at the map, the only thing that resembles a path next to the elite four would be Route 224.e

This route isn't of much importance and has nothing to do with the story line, but if you're really wanting to fill up you're Pokedex with CAPTURED Pokemon and you don't have a copy Diamond Ve rsion, than this is the only place in Pearl Version where you can catch Beautyfly.

Other Pokemon in this area include:
Grass
-Floatzel
-Gastrodon (Blue)
-Roselia
-Gloom
-Weepinbell
-Buizel
-Shellos (Blue)
-Chatot
On Water
-Pelipper
-Tentacruel
Fishing
Old Rod
-Magikarp
Good Rod
-Remoraid
Super Rod
-Gyarados
-Octillery
-Luvdisc

You can access Route 224 through Victory Road after you defeat the Elite Four.

-Hope this answers all your questions.

It is'nt all useless, but if you happen to have an Action Replay, you are able to get a Shaymin w/o going to an event. But if you don't have an Action Replay it's a great place to train and catch cool pokemon. If you do happen to hav an Action Replay post another question if you want to catch Shaymin.

At the right of the Pokemon League theres the route 224 that route is where the Legendery Pokemon Shaymin appear when you have the Oak's Letter. There some Pokemon and some trainer that you can battle.

Hope it helps!