OnApp allows uploading your custom bootable ISOs for recovery purposes. These could be different images for Windows/Linux/FreeBSD or any additional software. You can boot virtual servers from your own ISOs or the ISOs that are uploaded and made publicly available by other users. Currently, there is a limitation of 1 GB for the ISOs uploaded from the file system. There are no space limitations for the ISOs uploaded form the URL (except for your disk space limitations).