You can save the pictures to a suitable location on your computer. Then copy the text (highlight it and press Ctrl + C), then open Wordpad or similar and paste (Ctrl + V) it in. Then edit it as you wish. Save it if you want, or just select it and paste it back to a new Email and insert the photo if required. At least that's what I would do with Thunderbird, I'm not sure how you go with pictures on Google Mail.