Hello,
UHD and Ultra are newer resolution and most of the Dreams were made in HD 1080p
or lower resolutions ( older ones ).
Moving forward you might be seeing some higher resolutions , Stay Tuned ..
One thing you can do now on your own is fine some nice 2k and or 4K video on line
you really like and if you convert that video to WMV format you can play it in Deskscapes
just like a dream without having to convert it to the .dream format .
Be advised though it might run you CPU usage a little bit higher than a normal dream file.
But that's an option , Dream Maker is a Free download you can play with ..
AzDude
Stardock Community Assistant