Toilet tank cover sets can be 2 different things. It can mean the combination of the actual lids that cover the toilet tank and the seat, and it can also mean a set of wrap-around rugs that wrap over the toilet tank, the seat, as well as a rug for the floor at the foot of the toilet. There are a variety of options with either option you need.
Toilet Lids and Seats
The first thing you need to figure out before you can get a new toilet lid and seat is what size you need. While most toilets may look the same, sizes vary greatly, especially with newer, water economical toilets. Find out the capacity of your toilet, and use that to determine which lid and seat you need.
Wrap-around Rug Sets
Size isn't quite as important with the rug sets as it is with the lid and seat sets, because they are designed with elastic bands to wrap around the various components of the toilet, but you still want to make sure the set you get it relatively the same size, just to avoid excess around the edges. Aside from that, there are a huge number of sets and designs to choose from.