If you are already using a custom portrait, name the new image (jpg) using the name of the previous portrait, then use the console to enter ConvertPortrait name.
This will overwrite the file which you can then zip and host for download. If you are not using a custom portrait or do not want to overwrite the last file (you can give the old file a different name) then choose an image, give it a name and convert it as above. Then, contact a DM IG and tell them the file name. They can change your portrait, which you can then zip and host for download.
