I have a large thimble collection. I have bought many on ebay. I have them in thimble cases with a glass door covering them. Miles Kimball in Oshkosh, Wisconsin sells the thimble cases.

Lillian Vernon catalog has the type of shelf you are looking for...they have them for golf balls and baseballs and there is one that just has flat shelves...we collect shot glasses from different places we go and I needed somewhere to put them all and this works great...it would be perfect for the thimbles...they will even engrave the top for you...ours says Vacation Spots...they come in a few different colors of wood...