Have the option in Wiki.js's inbuilt media manager to upload and host your images or files on external image, video or file hosting services(such as Imgur, Dropbox, Google Drive, OneDrive, Flickr etc.) instead of storing them locally.
This would not only help people who don't have much storage space on their webservers, but it would also help with backing up files, and if you need to move your wiki to an other webserver you could do it without downloading and re-uploading tens or even hundreds of gigabytes of files.