Images used in custom mood themes must be hosted by a webspace provider that allows remote loading to LiveJournal.
but doesn't mention that the paid users who are going to be creating these custom mood themes also have access to ScrapBook, where they can store their mood themes.
So, something like this, perhaps?
Images used in custom mood themes can be uploaded to your ScrapBook. Alternately, they can also be uploaded to a webspace provider that allows remote loading to LiveJournal.
