Definitely a cushion.

Who sits there? Looks too small to be a window seat, except for dolls or maybe cats. I think I would finish it like a window sill and trim it out with some nice VG fir in clear stain and use it as a shelf. No sewing required. IMHO...The carpet is a bit odd and makes it look like a stair tread. Cute corner window! :D

Are you planning on actually using the ledge for sitting? Option 'C' might be to stain and finish a nice wood ledge!

I would do a cushion. Go on YouTube. You will find tons of great instructions on how to make a cushion. I learned how to sew thanks to all the talented people who took the time to share their skills on YouTube. It will also give you the opportunity to add a different pattern, texture and color.

If you carpet the window seat, be sure and add a steering wheel and rear view mirror.

Combine the ledge and new woodworking to make a built-in bench, sitting area that is big enough to enjoy. Just finish the wood with stain or paint and place seat cushions around.

My vote: No carpet.

Thanks for your help, though I'm not really clear on how Interiors International feels. LOL.

Good idea about you tube, pk. I'm wondering about cutting a piece of plywood or heavy cardboard and covering it like a dining chair cushion. That I've done before.

While I like the thought of finishing the seat with wood, I'm a little concerned that our small dogs would scratch it.

Aha! It is a dog seat! Whew, glad we got that cleared up. LOL... yes doggies need a little grip. 1/4" plywood covered with batting for cushion and cordura or canvas will work great. :)

The end result was an upholstered seat.

Is it that bad???

Looks like you did a nice job!

Get rid of the frilly lace valances. It is not the right look for that space. How about box valances instead using a complementary fabric to what you have on the bench ( but don't match fabrics).

Very nice!!!

What a fantastic change!

However, I do agree with laurae1967.