Well, it's easy for you to find out the exact date of your image files. I suppose you have saved them somewhere on your local machine.
On your Hazcom repository, do you have a "Sort by..." feature? If so, how do those files display there when sorted by date?
When you say "random order", do you mean that each time you view your Hazcom repository files through the moodle file picker they appear in a different "random" order, or the same order each time?
From my tests, it appears that the file picker orders files by date/time.
PS Pleaser remember to vote for bug report MDL-31406. The more votes a bug gets the better chance it stands of being fixed. You'll have to register in the bug tracker first, if you are not already registered.