Iconicity is when a symbol’s relationship to its referent (what it relates to) can be guessed, consider the ease of learning as this is important. A child may move from objects to photographs that have a particular meaning, but understanding
the concept may be harder.
Average symbol size tends to be 500 x 500 pixels (use points for measuring unit options) but this can vary especially when used in different settings or for those with specific pointing difficulties. It is therefore important to remember that
symbols will always need to be resized to suit individual requirements.
There should be clear outlines to all parts of a symbol. Usually these are black outlines around and within objects, faces and bodies from 2 to 7 points (although it depends on the size of the character within the image).
The style of the symbols needs to be consistent where
possible, with a understandable schema such as the one Widgit offer.
File names and symbol IDs need to be unique. Use vector files to allow for adaptations for example .svg with transparent backgrounds, but offer an alternative such as a .png. There may be a need to convert the images to jpgs and pdfs
for print outs of any size
Colour may be used as a border around a symbol cell or as a background to the symbol. Colour contrast levels are important especially for those with visual difficulties.