Bueno, salvo por ciertos detallitos, sería algo asi:
Estimated gentlemen, I'll try to be brief because I'm sure that you receive hundreds of emails.
The reason of this mail is that I need material of your website to be able to offer it to the users of my web totally free. When i say "material of your website" I mean the photos of anatomy (muscles) that I can find in (it). Can I use these images free also and expose them in my web?
Thank you very much for your attention, I'll wait for your answer.
Cordial greetings
Xavier G (SPAIN)