Yes. Zoomblr shows sequestered-jester's public posts and profile picture with no Tumblr account or login required. It's completely free.

Open sequestered-jester on Zoomblr and tap the download button on the avatar to save the full 512px image in its original format (JPG, PNG, GIF, or WebP).

Each image in sequestered-jester's feed has its own download button — tap it to save the picture in full resolution. Photosets give you a button per image.