When trying to send a text message to your e-mail account, enter the message content as if it were a regular text message. But when trying to send it, you would usually have a phone number in the "Send To" bar. Instead of a phone number, type in your e-mail address. The text message should then send to your e-mail.
Now, from the e-mail containing the picture you would like to send, you should just be able to save that picture to your phone's pictures/other memory. If not, copy the picture and paste it in an e-mail message going out to your phone. Instead of a regular e-mail address, type in your phone number. Once the picture has sent to your phone, you could then easily send it to your wife's phone.