We have an "Old Italian" Tuscan theme in our kitchen. Pictures & color are nice, but I wanted to go a few steps further.
Step 1: Build a Frame
Once you measure your entrance way cut out some plywood and screw some 2x4s onto the side. I used a hand saw to cut the 2x4s the same angle as the archway frame because my miter saw wouldn't cut an angle that sharp. You will probably want to use the frame as a stencil for your drywall before you screw the frame into the entrance way.
Step 2: Making your curve
I used 2x2s since I have several of them lying around in my shed from previous projects. This is a little time consuming. I cut them to fit the inside of the frame and went around the curve. I put a screw in each side. This seemed to be the easiest way to form a better curve. Once you finish that you can start putting on the drywall if you have room. You can always mud over the wood. I was working on 2 doorways and did things a little different with the second doorway. Since I will be painting a texture in the end it will not matter how rough it looks.
Step 3: Mudding Time
All you really need to focus on is filling the gaps.
Step 4: Place your tile
I mortared up the inside and placed the mosaic tiles. You can get all this stuff from Lowes or Home Depot. Then I placed the outside rectangular tiles. When I got near the top I had to start measuring each individual tile to cut it. I drug this project out for months and was able to let a lot of the mortar dry so I could keep going higher on the arch. I only had so many clamps to hold the tiles in place. Make sure you use spacers in between the tiles.
Step 5: Finished project
Remember to use grout once the tiles are dry and put a sealer on after the grout is dry.