However I think that portray is best kept to smaller / single things in the way that a portrait is a picture of a single person or family, whereas the rivalry between Russia and the USof A is a bit big to depict in a single entity.
"depitct" - again,this has a little bit of a precise feel to it. However, it can be used in a broader sense to mean "represent" which opens up wider meanings.
"illustrate" probably the weakest choice.
I would prefer "convey" since the topic is so big your image must select and area to work on or be suggestive rather than precise in its effect.