:: It is not necessary to use a giant package for the delicate mosaic...but it is important that it is immobile and rigid.
You will need:
A mailing envelope that's only a bit larger than your mesh mosaic. If it has padding or bubbles, even better.
2 pieces of rigid cardboard cut at least 1/2" larger than the mesh edge of your mosaic.
Strong tape (regular gift-wrapping tape is not strong enough)