Simply attaching an image in Gmail does not give you access to position the image in the email.
But through Gmail-Labs, now you can easily embed images in your emails (in between the content) just like you do it in MS Word documents or while writing your blog posts.
To enable this feature in your Gmail account, go to Gmail Labs, by clicking the green symbol at the top-right corner of the screen.
1. Inserting Images
2. Extra Emoji