I have same issues, but have noticed if I select one of the "missing" wallpapers (identified by the download arrow being next to the name) it will download but takes up to 5 minutes to finish downloading at 120Mbps download speeds; and then changes. If I swap to another wallpaper in the middle of the download; for example, in the Underwater section starting the download for "Humpback Whale" and then select "Jack School" before "Humpback Whale" finishes, it appears to pause the "Humpback Whale" download and only resumes when I select it again and leave it selected until it changes the wallpaper. A "Download All" option under each section would be nice and allowing the download to continue in the background, whether it is still selected or not would be helpful also.
I like the Shuffle All option, but would like the ability to Shuffle 2 or 3 verses all 4 (for example shuffle just Landscape and Cityscape) and/or the ability to select multiple individual wallpapers (for example, 5 from Landscape, 7 from Cityscape, 3 from Earth), a "Custom Shuffle" option.
The Shuffle Continuously has not seemed to work for me. I choose it and ran for a couple days and it did not change. Would like the ability to change it to a custom setting or every hour, 30 minutes, even 10 or 15 minutes.