the first and foremost task-addition of altcoins to your site
bitcoin only gambling is quickly becoming the thing of the past
look at all of the competitors-all of them have altcoin betting,many have more than just dice
the minimal set should be : LTC,ETH,DOGE,BTC this is what any modern site should offer in terms of currencies
not even talking about many other,not so popular altcoins (look at crypto-games.net for example)
every currency you adopt is a potential megawhale in this currency as your customer,paying for the wallets maintenance,support,database etc.

as for PVP/Multiplayer,meh only as a bonus for players,not very profitable imho and too much of a headache
if only you invent a surefire mechanism to make it a:provably fair b:cheaterproof c:interesting concept,so it brings profit and fun to play with your mates

improved livestats and graphs would be great,but again-not something you would want to see first on your favorite site