I have been wanting to make a dress for my dog, Beans for a long time and I finally gathered up enough courage to do it. I modified Simplicity's 4325 pattern for small dog clothes and came up with this:
I made my own ruffles out of some scrap fabric I had instead of using lace, and I didn't put any embellishment on the neckline. I got rid of the sheer overskirt and I added a sash around the waist (this was mostly to hide some wonky seams, but it works!).
Here is Beans in her dress:
And a closeup of the sash: