Just because he regrets it doesn't mean we can pretend it didn't happen.  It seems messy and confusing to have two different types of delimiter just because you don't like one of them but can't change it.  Well, you can if you don't combine the id and source.  My proposal didn't have this problem because I separated id and source into two separate properties.  That still works, with the only problem being it's harder to make a mulitple-file request without using JSON, but as I said yesterday I don't think that's necessary or really that useful.  I would suggest swapping the `:` (or `://`) for `/` in the single-file syntax, and using separate named properties in imageset for the JSON syntax.

If you want to stick with a single string that incorporates the source and the identifier, it must have a consistent delimiter.