Triptych – An artwork made in the form of three painted or carved panels
The paintings got a triple tick (triptych) from me because there were three panels.
Triptych is the same principal as diptych ("tri" meaning three and "ptych" meaning fold in Greek. Tri-ptych = three-fold).
Above is a triptych produced between 1425 and 1428 by Robert Campin.
Triptych art can be almost anything, so long as there are three panels or canvases. For example you could have one long image sectioned into three.
Three related images.
Three parts of a story or timeline.
Or simply a pattern.
You can also use canvases which are the same size and shape, or try experimenting.
If you're using card, you can use a hole punch along the edge of the card and attach them together with string or ribbon to give the effect of a traditional religious triptych.
Once you have chosen your canvas (or paper or panels) decide what your artwork will be of and which medium you want to use. Try sketching ideas onto paper first.
When you have chosen the image you want to paint, finalise it on your canvas and display it!