The best strategy is simply to play pairs if you can and play as close to the current card in play as possible. This means if there's a 5 in play, you should try to play a 5 as well. It ensures the lower cards are removed from your hand sooner than later.
So right now there is no incentive to not play in an ascending sort. Why would I play a 9 if there is a 1 in play? I have all those cards in-between in my hand I still need to get rid of.
The only ideas I have are:
1. Remove the ability for a 1 to defeat the 10 (or whatever's the highest card).
2. If you choose to pass, you draw the difference of the values instead of a single card. Example: if there is a 4 in play and the opponent plays a 7, if you pass you have to draw 3 cards.
There has to be something that gives people a reason to play out of order and there needs to be a little bit more risk-versus-reward here. Maybe another special card? I'd hate to do too much to the core rule set lest this game turns into Deuces.
Also, I plan on doing some actual artwork now. That should be a fun distraction.