After clearing cache for unsupported files, does this also clear photos from cloud or do you need to do something else. As I thought once deleted it means ripped up shredded burnt thrown away... not to be seen again..
Welcome to Android Central! What device are you using? What do you mean by "clearing cache for unsupported files"? There are app caches and the system cache partition, but there isn't a cache for unsupported files. Which gallery app are you using?
An "unsupported file in Gallery" normally means a file that's not of the type that Gallery can display ... and Gallery should never load those file names from the list of files it gets names from, so you should never see that message. It could be that the file is corrupted, so you only see that message when you try to view that file.
Clearing the cache has nothing to do with the files in the cloud.