Tapes can be used as both elements & tools in your mixed-media art. Apply masking or duct tape to a piece, then rip that sucker right back off. Instant distress; that's a tool! Now more than ever, there are dozens of tapes for every use imaginable. Those are elements! A few are manufactured specifically for artists: book binding tapes & Chartpak Graphic Arts tape. Double-sided is primarily used by artists. Gaffer's tape was originally designed to hold down cables, wires, props, etc. for concerts, stage productions, movie sets, TV production, & photography but having been
co-opted by scrapbookers, it's now available printed with intriguing graphic designs & evocative words. Scrapbooking supply companies also manufacture a decent array of decorative tape styles including floral, Rococco, & scenic. They have the advantage of being acid-free, so when you incorporate into a piece, you know they won't discolor or disintegrate (like old transparent tape - although I actually love that look & have chosen to replicate it on some of my own pieces. You can spray with a fixative to eliminate further disintegration.)
Heidi Swapp, Prima, & Two's Company all include tapes in their product lines.

A partial list of other tape types includes:
--Duct & pipewrap
--Electrical insulation
--Masking - General purpose, industrial grade, indoor or outdoor, & high temp.
--Colored masking tape is used for color coding, marking, book binding, & other general uses. It's one of my faves; it comes in a variety of colors & widths, you can get it at any market or hardware store, & best of all, it costs next to nothing!
--Marking tapes are used interchangeably with gaffer tape. 
--Barricade/caution/crime scene - a specialty tape that's not for everyone, but will add a real graphic punch to your art! Can be found either sticky back, or as non-sticky 'ribbon'.
--Carton sealing - paper (draw, print, or stamp onto it), strapping (filament), clear (use for making urban grunge style photo transfers from magazines & catalogs), & decorative 
--Fluorescent spike tape is used in theatrical productions to mark the stage.
--Foil - copper & aluminum tape for industrial use; also manufactured in various widths for soldering. Also, decorative colored foils. 
--Vinyl - available in an array of colors
--Polyester film tape also comes in a variety of colors, most commonly red. It's typically used in film splicing & leaves minimal residue on removal. 
--Grip tape is available in every sporting good store.
--Surgical tape
--Don't forget Sticky Back labels - while not officially 'tape', they can be employed in a similar manner; many have very cool graphic borders.