The above picture is a generalized overview of most wine bottle sizes. Some wineries do change they're bottle lengths, widths and styles, but on average the above picture is accurate.
There are essentially only 5 sizes for wine crates, Magnum being the most commonly made size. This is followed by Double magnum, Jeroboam Imperial and Single bottle (750ML).
Where are the single bottle 750ML crates? This bottle size is the most common made by wineries. They don't often make single bottle 750ML crates because they're small enough to be packaged together in 6 and 12 bottle cases. The other bottle sizes are so large that they need they're own crate.
Average dimensions of these single bottle crates:
Single Bottle: 13" L X 13" W W X 3" H
Magnum: 14" L X 4" W X 4" H
Double Magnum: 15" L X 5" W X 5" H
Jeroboam: 17" L X 6" W X 6" H
Imperial: 20" L X 8" W X 8" H
Except for magnums, we generally have to custom-make crates for larger bottles. Most of the Jeroboams and Imperials are rarely made by wineries. Generally they're reserved for private collectors or given as gifts to top selling stores. You may find these crates in the windows of very fine wine shops. They're really big!