You can upload several types of virtual machine image formats to Stabild: qcow2, iso, vdi, vmdk, or img (raw) formats are supported. Note that the image file extension MUST be one of the above.

You can either upload directly from your local hard disk, or paste in a URL and upload from this, e.g. a direct link to file from Dropbox.

The URL upload feature works by simply typing in or pasting a URL, and hitting “Add from URL” and then “Start upload”, once the URL has been validated. You could try the excellent ISO images that Turnkey Linux makes, a plain Ubuntu or Fedora server,  an image you have uploaded to your Dropbox account or this CoreOS ISO: