You cannot upload photos in the csv file. However, there is a way to achieve what you want. Follow these steps.
Step 1 - Upload all photos in bulk using the zip file upload feature - https://support.prosale.com/hc/en-us/articles/360043274231-Upload-Inventory-with-Pictures-in-a-Zip-File-to-Create-Inventory
Step 2 - Export inventory to csv using the import/export feature
Step 3 - Open the csv export file on your desktop and change the pricing, category, description, and other details of your choice. Just make sure you do not change the Stk/Sku number.
Step 4 - Use the import/export csv feature from the inventory tab to upload the updated csv file. This will overwrite the name, price, category, and description that is associated with the same Stk/Sku number.