>>115746
As many as feasible. Something like the character creator I posted in the OP would be a good start, maybe skewed a little away full realism. Beyond that just options like like a choice between human hands/feet, paws but still plantigrade, and full digitgrade. Or multiple coat colors and paterns. It doesn't have to support sparkle dog level, just a good selection of all the colors and paterns that you can find in nature.
Nose, paw pad, tongue, etc coloration would would be a good choice to have too. In fact you could go a little wilder with the color choices for skin since that tends to have a possibility of being more shockingly colored than fur is. Just look at some types of baboons or birds. Good height sliders are important too.
In general I would rather have sliders than to just pick and choose features from a list. That gives you better control over your character and makes it feem more like yours rather than a fancy Deviantart character generator.