A photo captures the food and also the atmosphere of a place through even the subtlest expression of its presentation. Just look at this photo from minimal. Not only does the crawfish look deliciously seasoned but from the plastic bag presentation you also get a sense of the casual vibe of the Crawfish House.
And from the rustic wood table, hearty slices of bread, and bistro porcelain bowl in this picture of the gazpacho from Le Pain Quotidien, you can see the focus on artisanal breads and the café setting.
But I know how it is. Sometimes you write a review and your camera, which holds that photo you took, is in your car or at the bottom of your bag. No worries. You can easily add the photo later (as well as edit your review) by clicking on the “Edit Your Review” button on the restaurant page of your review.
And as always, please photograph your food responsibly. No flash (which is just rude) and no photos of other people (because you may have eaten at Pink's in Hollywood at 1 a.m. on Saturday night but there are others who may not want the rest of the world to know they were there too).