Email can be sent as "Plain Text", HTML or maybe "Rich Text" (if you are using Microsoft products like Outlook and Word)
The person receiving an e-mail can set their email system up to receive e-mails as plain text, or HTML or rich text.
So if you created an email in say HTML format with fancy fonts, colours, graphics etc, if the person who got it had their system set up to recieve "plain text" only then they would not see any of the fancy colours, fonts etc.
Try setting your email system as "plan text" and send the pictures as attachments (rather than in the body of the email)
The person getting the email will then get them as attachments.
More here:
http://tss.oregonstate.edu/cn/soft_tips/docs/o utlook/?page=mail-format&type=normal
http://email.about.com/cs/netiquettetips/qt/et 070103.htm