It only runs once a day....
So it downloads a wallpaper and applies it. Then the next day it does it again but overwrites the first.
When I tried that it just overwrote the file with _%DATE in the name. :P
Sorry but there is an issue with the forum where it can't send out emails.Because of this the forum is in read-only mode at the moment.
You can find the currently known issues with Tasker and possible workarounds here.
Separate names with a comma.