I have one of these in the bathroom that predates us, and I always figured the only option was replacing the tile. I'm curious to see the answers, too.

If the cracks are in the tile themselves. There is no way to correct this as it is a sign that the tile moved or is moving. Any paint or epoxy that could be used to fill these cracks would fail in short order.

Also any repairs would have to be an exact match to color and to gloss. If it was not, the crack would show up even worse then it does now.

Crack in grout can be repaired by "sawing" out the old grout and re-grouting...cracks in tile your pretty much SOL

here is an article I wrote on tile repair tips...it basically covers replacement ideas + options

http://www.networx.com/article/cracked-tile-...

We have the same issue with some tile between the kitchen and family room. Our tile is an off white/tan blend. We filled it w/some light paint and you can not notice it, unless you are looking for it.