The only way I know to shape tile is to use a tile saw. I have a Taurus 3 ring saw that I can use to cut any shape in either tile or stained glass. It's slow work, cutting tile, and the replacement blades are expensive. If you wanted to cut stained glass into shapes, I usually use a Toyo pistol grip glass cutter and I can score the glass with that and then break it with a Fletcher tool.

Mattie. as Silva says, its tricky but you can do it with nips if you understand that you can only "chew" your way to the edge and not cut anything out really. I think of nippers as nibbling away excess until you get what you want... its not perfect and it does take time to develop the skills reliably.

you are less likely to make a curved break if your cutting edge is perpendicular to the tile face and not leaning away or toward the tile surface.

Thanks ladies, working with (ceramic) tile is quite different than glass so it is a learning experience. Working on a small mural, will post pictures later.