Dee, it would be impossible for anyone to draw up plans for a generic window seat that would hope to fit more than a few windows and decors. That's the bad news. The good news is that building a window seat can range from very simple and inexpensive to elaborate and expensive. One real simple approach is to just build a plywood box, paint and have a pillow made. Another idea is to search the web for outdoor furniture plans and adapt a design for your window. Or just build a frame from 2x4s to the size you want, screw the 2x4s to the floor and overlay the frame with plywood or MDO. Use plywood with vaneer to match your molding or furniture and stain or paint the MDO. If you plan ahead, you can add a hinged lid for storage under the seat. An upholstery store can make a pillow for the seat or tell you where to have one made and, again, the pillow can range from relatively cheap and durable to expensive. But your house, taste and budget will lead you to the right answer for you.