I was testing
MDL-33453, creating aliases from filesystem repository when I noticed:
1) Create a folder, and add contents to it. Then pick the same image file TWICE, as alias, from one filesystem repository. The first alias properly show the thumbnail of the image, but the second, after replying that you want to rename the file because it already exists, does not get its thumbnail created at all. Note I've not tried other sources different from filesystem repository, perhaps this problem is common to all them, always the "do you want to overwrite..." dialog is shown.
2) Looking for information of "filesystem-source" aliases, I get the "Original:" information empty. Always. It seems to work ok if the aliases are from "Server files" repo. I see briefly the "progress animation" and nothing is shown at the end. I'd expect some path within the filesystem repo to be shown or so.