Hi,
Dopus image viewer uses white background. This is quite annoying, especially when I try to preview white images with transparent background. Please make background as checquered (solid color is usually useless with said transparent bg images)
You can configure the background colour via Preferences.
There's no option for a chequered background at the moment, but you can use Shift-A (or View -> Hide Alpha Channel) to toggle the alpha channel on and off to see what is/isn't transparent.
You can change the background colour.
Preferences
Viewer
Viwer Pane
Picture background color.
So really you have a "feature request".
"Please (always helps) can I have a background picture." might work.