I did trim around an egress window in a basement once (just a test) by screwing a 2x4 around the wall next to the window, then covering with drywall. Definately gave a different look to the window. There's many things that can be done with drywall to give windows a different look.

Bunt

I haven't read all of the replies to this thread; (it's pretty long, and I only have so much time). So this idea may have already been addressed. But I thought I would suggest a method to trim the inside of the windows that might work well for you. This works quite well if the depth of all extension jamb points are fairly consistent.
We typically measure all of the extension jamb needs for consistency of dimension. We want to rip the jamb stock to just touch, or slightly brush the window itself, perhaps leaving up to 1/8" space between the two. Then we rip all of the extension jamb stock, make up the jambs, case them, and then set them all in place preassembled. With such a deep jamb, it usually is wise to place some blocking around the opening near the window to guide the jamb into place, and to ensure a consistent reveal, jamb to window. Then if you like, depending on the gap between jamb and window, just caulk the joint, and your done! This method works well, looks good, and is very fast, and very consistent.

Best to have a window with "drywall return flange" option. Then the jambs slide inside a channel, instead of butting up to the window. Caulk prep paint and allowances for inconsistent window installations is made easy.

For a sweet finish option, get your cabinet maker to make and case all the boxes and casing the same finish as your cabinetry, they come to the job two days prior to closing and install them. No coffee cup stains on your drywall sills to clean up!!!

Or slick finish drywall returns sides and tops gloss white with "concrete countertop" sills is also an excellent way to finish

Marvin Integrity has the flange option, also Superior Seal in Southern Ontario.

Kevin

I saw some stuff at the lumber yard today I didn't know existed. Three versions, SpreadStone, SpreadRock, and RollerRock from daichcoatings.com. I'm thinking that it might look interesting and pretty good if I do a drywall return on top and sides, put a 1 x 4 trim around, and then coat the return and trim with SpreadStone. The idea would be to have the look of stone surrounding the window. The instructions show how to use stencil tape to create the appearance of joints. Might be worth it to spend a few bucks to do a mock up.

I've sent an inquiry to them to find out if it's practical to use the stuff to coat ICF between ground and siding.

I've used widnows with drywall flanges before (they were vinyl). The flanges on the windows I used stopped about 2" short on all the corners, so you could still see the drywall butt to the window in the corners. Also another nice option expecially for the kitchen window is to use a marble sill. I think I spend about $30 on the last house for a nice marble sill. You can either have them cut sill, or any tile saw will do the job since marble is so soft.

Bunt