Yes, I did, just as easy as embroidering cards and same considerations: not too dense and relatively long stitch length, but less critical than card stock - good quality wallpaper does not tear so easily along the stitches. I particularly like designs like the one below, those work very well. I never tried 'normal' filled embroidery designs.
Thanks mops, my hubby went to the paint shop recently and they gave him several discontinued wallpaper books for our granddaughters kindy, and it just gave the thought as the size was right and there was so much variety, did you hoop the paper or just float it?