As long as the tokens you are storing is an ERC20 token, you can store any amount of tokens in MyEtherWallet.
The tokens that you add in the wallet appear directly in your wallet if they get listed.
The tokens not yet listed on any exchanges can be seen through the ADD CUSTOM TOKEN option in the wallet which has no limit.
this is pretty cool.. But I wonder why Bitcoin is not used like this? Is this one of Bitcoin's limitation or simply the choice of developers?