Totally agree with you on the Mug Rugs!
Or even a bit bigger as vase mats?
And in another twist ... you mentioned pot holders ... my mug rugs double as pot holders!
Or perhaps, simple placemats for humans? Even done as singles, rather than matchy sets!
How about? ..... dog/cat placemats? for under their food/water dishes?
CJSews' neckerchiefs would be ever so popular, I'm sure.
While the first thought is towards animal themed prints and items, I don't think it "needs" to be just that. Of course, that might be one of the pre-requisites for the contributions.
Have my thinking hat on for other simple contributions that could be great $$ generators! Looking forward to seeing what other ideas come forth!