There are two things to look out for when picking a paper or sticker to emboss.
The first thing to look out for is printing. We recommend embossing on unprinted materials—if there's an added lamination or color, the edges of the embossed area could break through that additional layer. You can tell if there are added layers if the two sides of the material don't match.
The second is thickness. Your material shouldn’t be thinner than printing paper because the embosser could break through the paper. On the other hand, anything thicker than a standard cardstock could be too thick for the embosser to make a clear impression.