custom smilies

I want to add edit existing smilies, but if I edit one, then I either get the error: Please enter a valid emoji short-name or image URL. Yet, the smiley already has an Emoji that works. Its just that its parsed into an image. Deleting the image from the field and entering the short code...

Allow user use their own smilies in your forums. Permissions: Limit the number of smilies which users can own Bypass smilie size limit Can use smilies from other users Images supported: PNG JPEG, JPG GIF

When you open the smilie container of custom images in your custom smilie tab, how can you make it so the image size in these containers are small and then when you enter them in the post it goes to it's actual size?