The most important thing in my view is that all blocks are similar to the original minecraft texture (nothing too crazy). Back in the day i used Gerudoku pack then stopped using textures due to all the updates but recently found a really nice take on the original minecraft texture and makes the whole game look much nicer without much change. My vote therefore has to go to this pack that i use called traditional beauty.
http://www.planetminecraft.com/texture_ ... al-beauty/
Also would it be possible to somehow force players to use the server texture as this would finally put an end to texture x-raying.
I would also say that as we are aiming for a mainly vanilla experience, using the default texture would also work and i would support that.