Thank you! Do you have Pinterest? There are lots of examples there.
https://www.pinterest.com/search/pin...tained%20glass
But faux stained glass is basically a special type of translucent paint you paint onto glass. Like real stained glass, you do the black lines first (called the leading, or leaded line). It looks similar to puffy paint. After the leading dries you color it in.
If you can trace, you can do this. There are lots of more geometric designs that you can do if you don't want to do a picture. One minus is the color dries very light, and for the most part, I went over the peacock three times. If the paint dried darker it would have taken me three days (incl the drying time) instead of a week.
This is the kit I bought.
Amazon
If you want to do a more geo pattern, you can get the leading that come in strips like this.
Amazon
Then fill in the blank parts with clear and it will make a wavy look when dry.
The best part is if you don't like it you can peel it off.
I taped a picture of the peacock behind my glass. Hopefully you can get to behind your window so you can tape a design in the back. If not, then freehand a more simple one. I'd love to see what you come up with if you do it.