Image file type = what kind of image file type are they uploading? Accepted image file types include .jpg, gif, png
Image file size = how large are the image files? Default maximum file upload size is 2MB. I know of some members who tried to upload images from their digital cameras which were way too big.
They are trying to upload JPG and PNG. I can’t upload photos that are too large — over 2MB, but some of the other users can’t upload anything. I have emailed them files that have worked for me; a PNG 200px by 200px and a JPG 500px by 500px and they won’t upload for them. I don’t understand why a file would work for my regular user account (not admin) and not work for other regular accounts.
I found out that in my case when you upload a file with extension .JPG (capital letters), the upload will fail. However, when you rename the file to extension .jpg (small letters) the upload works fine. I do not know yet where to change allowed image file types and add .JPG (capital letters).
Found the answer in this thread: https://buddypress.org/community/groups/bp-album/forum/topic/upload-size-limits/
So, to be able to use upper case extensions go change line 525 in plugins/buddypress/bp-core/bp-core-avatars.php and change
(jpe?g|gif|png)
to
(jpe?g|gif|png|JPG|GIF|PNG)
(change it twice in that line)
Hope this helps!
This should definitely be a part of the core. Thanks for coming back and updating this thread 
It looks like the issue is still there:
http://pastebin.com/zGivLaZn
