I love the simple style of the Shikisai. While they've got sketches for adults and toddlers [1], check out their pet line (extra-small to large). Using just black ink on white background, the shirts all feature line drawings of ordinary objects. While I'm not sure I've got the extra $30 [2] at the moment, put this one on my list for things I'll invest in when the economy picks up again. I'm doodling just thinking about it.