I personally use FaithfulVenom 32, it's not particularly laggy, stays "Faithful" to the default themes and textures, but is slightly more HD, and has nicer colors. IMO, I find the default colors a bit dry and bland, FaithfulVenom changes that.
One thing you want to look for in a PVP Resource/texture pack is the fire - Not laggy, and not tall. You don't want it blocking your screen.
Also, clear water if at all possible is a good thing, better for shooting and picking up items that drop in water.