Most artists use them as something developed within the sphere of their own work. A motif can be idiomatic, coming about as an artist's work evolves and becomes more specific to the artist; an expression of their own creative "voice".
I started thinking about this while preparing for the Creede Quick Draw. Unlike most of the plein air quick draw events that I participate in which are about an hour and a half and require the artist to paint from the view, the Creede Quick Draw is only an hour but allows artists to paint from a sketch, or recreate something that they had painted previously. It is a good opportunity to do a painting that is memorable and distinctly "me".
This got me looking for themes in my own work and compositional ideas that I have used over and over: aspens in the woods, cotton wood trees, deep forest scenes; these are compositional ideas, or motifs that I like and return to.
For our class sessions I came up with 4 compositional motifs taken from my sketches, and we used them as a starting place for small 6"x 6" paintings. The great thing about these is that once the shapes are established, all kinds of things can be changed to create distinctly different paintings: a high or low horizon, light direction and value variation, color or season change, the addition of other elements.
With the two bottom sketches I have shown paintings that were created from them. The Aspen and Pine piece is my 10"x 8" Quick Draw painting from Creede using the Aspen sketch. The idea of a small stand of aspens together with pine trees is something I see all the time and creates a naturally strong value sketch. The other 2 paintings are based on the Cottonwood Grove motif. One painting is vertical, one horizontal and they use very different color and levels of stylization, but both reflect the same compositional motif. Cottonwood trees grow in groups like this all over the San Luis Valley and I use them as a theme in my work with a compositional motif that is very adaptable. I look for these compositional motifs in the landscape. It is one way I have used composition and regional elements to develop a more distinctive painting voice.