I know we all like to have a resolution and a proper answer to all issues but I can't be sure why this would happen.
I'd recommend uploading the images in an order like
Subfolder called images or imgs etc
And then short/sweet or detailed files names involving lowercase or numbers only.
Once complete take a backup of your website - 10 seconds and then in the future if this has happened again please contact us.
Since you are on the old panel it may be of use to visit www.000webhost.com, create a new account with new email so you can re-upload the backup you've taken onto the new platform and hopefully it will be resolved finally.