All flower gardens need butterfly visitors, so here are packets of 5 pink enamel butterflies. They are 22mm x 10mm and zinc alloy backed. They have a link which can easily be snipped off with a pair of pliers if it pleases you.
With really flat tesserae like these, I usually glue something to the back of them. Usually a large seed bead, or even just a blob of thinset. This is to give it some height, so it doesn't get lost in your mosaic. Alternatively, these kind of tesserae can be glued on after a piece has been grouted and cleaned.
Don't be limited by your materials, play with your tess-array.