i have got some tips for cutting glass mosaic ,if it is 20 x 20 and comes on a sheet you can cut these with a grinder with a diamond wheel ,the trick is to double fold some cardboard and place the sheet of mosaic on this, place a wooden batten over the sheet of mosaic for use as a straight edge and to pinch the tesserae so they dont move about when cutting, cut the sheets ,the vibration is reduced cutting on the cardboard and less tiles shatter when doing large scale mosaic jobs corners reveals and window heads are better built out to the full cube either with plaster board ,backer board of if you are really clever, rendering, edges and corners can be polished using an edge polisher and carborundum pads going from 60 grit to 220 grit, rubi are now doing mosaic ,wheel type ,nippers for around £25 these are good for cutting in small amounts of tiles but for floor to ceiling cutting use the grinder method it is much quicker ,as you all know preperation is the key to good mosaic work the flattest ,plumbest walls are needed for best results