Some craft stores have a "peel & stick" leading, then use glass paint inside the leading. The leading can be formed in any shape easily. My daughter used this on her bedroom window several years ago, and it's still there! The glass paint can be blended; you can use different tools to create texture. (One example used a regular hair comb to create a wavy pattern - it was cool!)
Go to https://plaidonline.com/brands/gallery-glass to see their products. I also found an article on using the paint at this site, but as it took me awhile to find it, here is a direct link.
Hope this helps!
Julie Burton
Moderator updated dead link.