You can add author photos to the Press Kit section of the NetGalley title record.
On the TITLE DETAILS page, at the top of the left-hand side you'll see TITLE DETAILS, and under that Title Information.
Simply click the orange arrow next to Edit Marketing Details and scroll down to the Press Kit section at the bottom.
From here you can browse your computer to find and upload files to this section, and also add a text description of the file (e.g, Press Release, Exclusive Interview with author, etc.).
The following file types may be uploaded: .PDF .JPG .JPEG .GIF and .PNG. The maximum file size allowed is 1 MB.