Blue Iridescent Glass Mosaic, Home Depot, $4.99 sq. ft. (according to the reviews, this is actually blue and a fair bit of copper -- if it looks notably copper, that won't work for us, since we're doing chrome/nickel elements elsewhere in the room, but perhaps it will work for one of you someday):
Merola Lantern Blue Glazed Porcelain Moroccan Tile, Home Depot, $9.05 sq. ft. (pretty and with a cool Moroccan feel, but maybe too grown-up for a kids' bath?)
I swear, I went to Home Depot and looked, but I didn't see any of these -- should have checked the website. Pam says the Lincoln Park store has the best selection, so I may drive by there sometime this week.
I have stayed at hotels a time or two with the Merola Lantern Blue Glazed Porcelain Moroccan Tile (or something very similar) in the bathroom, and I did not like it at all.
However I suspect my unsupported opinion here has limited value…