In 'Ctrl+2' view mode, you can see q'ty of items in folder, so see if it empty, is easy.
But in 'Ctrl+1' mode, not.
In this mode, if same number (items q'ty) display directly on folder icon, in right low corner, it is nice? May be it good idea?
What about having the default "Full" icon to be like the Windows "Documents" folder; with somethiing showing it's clearly full.
The same icon without the paper in it could sigify it being empty.
Most importantly:
If you have hidden files showing, hidden files count as content.
If you have hidden files not showing, hidden files don't count as content. But trying to delete the folder should throw up a Windows-style question reminding you that there are hidden files and do you want to delete them as well, or see what they are.
You could display a number on the lower left corner of the folder for number of files contained therein. There would have to be a maximum cutoff number with just a + after, ie. you would not want to have a 34 digit number! So maybe just 500+ as the number of files inside the folder. A good way to represent 0 files is just 0. How about a sly way to represent hidden files? Just use a negative number! A folder with no content except 8 hidden files would be represented by -8. A folder with 1 nonhidden file and 8 hidden files could be represented by 1. Or, you could just have 8/500+ to represent both hidden and nonhidden files. An empty folder would show 0/0.