I'm listing categories & when you choose individual items from these categories, your list will become Huge ;-))) Moreover, you can choose from various categories to make your drawing tell a "story".
And you can change the same drawing by using different media or by changing perspective, distance, lighting, angle, genre, etc.
- the sky [ day & night sky] -- sun, moon, clouds, stars, ......
- the elements - rain, fire, water, land, ....
- beaches - sand, oceans, surfers, shells, driftwood, tides, ...
- aquatic life - algae, whales, sharks, octopus, coral reefs, deep-sea divers, ....
- islands, boats, ships, nets, trawlers, anglers, ....
- still-life -- any & all objects at home, using different light sources & perspectives, shadows & reflections
- yourself, friends & family - portraits, caricatures, ....
- nature from your window -- trees, neighborhood, lawns, birds, ....
- animals, including pets
- birds
- plants, trees, flowers, bees & butterflies.....
- humans performing various activities – series of dancers eg.
- transport systems - bus, car, train, plane, spaceship, UFO, ....
- architectural marvels, buildings, sheds, ....
- dreams & fantasies
- mythical & mythological forms/creatures
- mountains, rivers, landscapes, .....
- anatomy
- any congregation of people/animals like circus, zoo, fair grounds, etc.
the list can go on & on ;-)
http://painting.about.com/od/inspiration/l/bl-Painting-Ideas-Machine.htm
AND http://www.magatsu.net/art/index.php generate random ideas for free
http://www.newscientist.com/imagegalleries -- this site has a weekly (or more frequent) “Picture of the Day”
http://www.stumbleupon.com/su/2ctS4a/www.nisk.k12.ny.us/departments/art/sketchbookideas.html -- 149 ideas for a sketchbook
http://schunnin.blogspot.com/2008_11_01_archive.html -- use these “challenges” to create your own versions &/or think up similar challenges for the future.
http://moonmaiden.hubpages.com/hub/1000-Random-Things-For-Sketching -- 1000 random things for sketching
-- http://www.kerismith.com/wp-content/uploads/2010/06/100ideas.pdf -- I like the idea of making your own paper cuttings with tips & ideas. You can fold & collect them in a jar [like a wish jar] & pick any one randomly & implement the idea. It can be like a never-ending stream of ideas if you keep adding to the jar whatever you find amusing, creative, any idea, website, activity, project, etc. etc.
You can Combine 2 or more prompts/ideas to create New versions :-)
In general :
-- Nature, the great outdoors, the scene from your window, anything & everything around you, ....can tell a wonderful story.
-- You can also try to visualize quotations, lyrics, jokes, quips, literary characters & scenes [from any book you are reading], etc. - give it your own interpretation & impression.
-- Ask "what if....?" questions. eg. What if we had only 4 fingers in each hand? What if the stage curtain does not drop at the right moment? What if a character from Shakespeare met a character from Victor Hugo?.... When you think up answers to some of these Qs, you can get some unique material for your drawings.
-- News items, current events, human interest stories, weather, etc. also offer you a Daily opportunity to draw something.
-- Dreams, fantasies, interpersonal experiences, feelings & emotions, colours, ....
-- From A to Z, think of a thing starting with each letter every day & draw it. eg. A for apple, apostrophe, apparition,... today ; then stuff with B tomorrow; & so on. Think of more than one thing, that will go together meaningfully, for each letter, & compose your sketch.
-- Similarly with geometric shapes. Choose one & develop some images with it.
-- Visualize & draw Emotions / Traits, etc. eg. Courage, Love, Fear, Hate, Perseverance, Peace, Joy, Kindness, Naivety, etc.
-- You could also depict Life stages or Rites of Passage such as Birth, Death, Adulthood, Maturation, Childishness, Teenage years, Mid-life crisis, Old age, Senility, Marriage, Widowhood, becoming a grandparent,....
-- You could think of some "story", incident, issue, quotation, joke, ... & try to depict them through your sketches.
-- You can choose characters from any book, comic, film, poem, etc. that you like & develop them visually. Draw them as you "see" them.
-- Mythological characters, symbols, ...
-- For any or all of the above, you could do a whole Spectrum of emotions, expressions, positive-to-negative, and so on.