BuddyPress.org

It looks to me like you were storing images in the buddypress/bp-themes/bp-default directory, which gets overwritten whenever you upgrade BuddyPress. It’s a good idea to create a child theme for bp-default and to make all of your edits there. I see you’re using one called BuddyPress Colours Aqua; you should store all footer images in that directory, so that you don’t overwrite them when you upgrade BP.