Yes, if I didnt say it clearly enough, "starcraft cuts image into 4 even columns and 8 even rows" (i.e. 256[width] x 512[height] image would be cut into 64 x 64 rectangles). And the size itself isn't restricted in any way, but the size of borders in game will be relative to the size of the image.
If you ever wondered how to make your own dialog background without stretching image to fit, here's how you need to format image to be properly setup it as background.
When you input file to be used as background image, starcraft cuts image into 4 even columns and 8 even rows.
In first row, every column is each corner.
Second row is top border, 3rd bottom, 4th and 5th are right/left (and will get rotated 90 degrees clockwise).
Not really sure how exactly it cuts background from the column in 6th row, but your best bet is to use one color there.
Image presenting how sc2 changes image into dialog background below. I've used 200x200 image there, but note that border size is relative to the image size you import. If I used 400x400 image, my borders and corners would be twice as large, and if I'd make image 200x400 (width x height), my corners would be twice as tall, and all borders would become twice as thick.
After you make your background and import it to you map, just use this action to change you bg and it should fit any dialog you make.
Dialog - Set the background image of (Dialog) to [Yourimagepathhere]
Yes, if I didnt say it clearly enough, "starcraft cuts image into 4 even columns and 8 even rows" (i.e. 256[width] x 512[height] image would be cut into 64 x 64 rectangles). And the size itself isn't restricted in any way, but the size of borders in game will be relative to the size of the image.
If you ever wondered how to make your own dialog background without stretching image to fit, here's how you need to format image to be properly setup it as background.
When you input file to be used as background image, starcraft cuts image into 4 even columns and 8 even rows.
Image presenting how sc2 changes image into dialog background below. I've used 200x200 image there, but note that border size is relative to the image size you import. If I used 400x400 image, my borders and corners would be twice as large, and if I'd make image 200x400 (width x height), my corners would be twice as tall, and all borders would become twice as thick.
After you make your background and import it to you map, just use this action to change you bg and it should fit any dialog you make.
Dialog - Set the background image of (Dialog) to [Yourimagepathhere]