Here are three links to writing a visual analysis. Remember that I am both interested in you learning how to write and make arguments about visual text and in you learning how to apply strategies for writing and discussing visual text to writing and discussing about other texts. To that end, the first link is favorite link. The last one though is very good for quick reference about vocabulary common to visual analysis.
“Visual Rhetoric: Analyzing Visual Documents” Handout, Purdue OWL, Purdue University
“Visual Analysis” Handout, Writing Studio, Duke University
“Visual Analysis Tips” Handout, Art History Department, Skidmore College