How about making a special Vendor that would sell things for "PvP Tokens" and "Battleground Tokens" ? For example, 10 BG Tokens for 1x Custom Gem,100 PvP Tokens for 1x Custom Gem.
It can sell seriously anything, it's just that when you're full and like to play some BGs, you don't really have any use of Battleground Tokens and PvP Tokens. Would be cool to have something like that.
NOTE: Amounts of tokens I wrote are just example, it's up to you how much it would be.