I am having issues with the SKIN URL as well, and including the steve.png in the resource pack ends up turning out very badly!
If I remove steve.png, everything displays and works properly except for the SKIN URL component. Perhaps it's because I'm using HTTPS on my Dropbox account (do you need http:// or https:// in that URL?).
Is this because MPM2 is expecting the default 16x steve.png and it's getting a 64x steve.png from the Soartex pack I am using? Can this be fixed?