Likewise. A bath mat. I've never heard of a "bathroom mat". I've also never heard of a "bathroom rug" - a rug's a rug.I would say "bathmat" not "bathroom mat." To me, a bathmat or should it be a bath mat is a smallish mat that you put next to the tub or shower to step on when you are getting out. A 'rug' is just a rug somewhere in the bathroom and not necessarily next to the tub/shower.
Internet Advertising and Selling 101:On walmart.com you can find results for both expressions.