Symbols in visual art are like those found in literature and music and also mathematics.

In algebra we use numbers all the time - even though we don't know their value. We know that if we have three of a number it's 3X - a number times itself is x-squared - and we can make images of them.  We can talk about many attributes of a number while it is still just an 'abstraction'.

When making 'abstract' images - or 'non-figurative' images one can give meaning by using  symbols as well as our cultural associations to the art and design elements.

Anytime one sees a heart, for instance, we get a clear meaning. But even circles evoke meaning - it is complete, whole and has not corners. All shapes evoke some kind of meaning from associations.

Using the art and design elements we can also easily convey meaning -  using scale big things seem grand, small things intimate. Lots of movement feel energized or busy. Strong contrasts can evoke feelings of tension.  Color temperature can be easily associated with mood as can different kinds of lines and shapes.

Look at the paintings below from the middle of the 20th century and see how they 'feel'.

Robert Motherwell

Bryce Marsden

Using an analogy from music think about how Leitmotifs can provide meaning in music. for an example of this think of the themes in Star Wars - click here for a Wikipedia article.

Notice the paintng by Pierre Bonnard - he is using pretty much all primary colors to create an image of very bright light. This is called impressionist color. The idea is to create an illusion of more light.

notice how this is different than using tints and shades - adding black and white - this is by Pieter Claesz 1628

characters put into a cell. Note the detail on the trees.

check out this link for more on Evyind Earl Disney work.

link to Wikipedia article on Jan Vermeer Dutch painter 1632-1675. Known for masterful depiction of light.