There has to be a quicker way than this, but this seems like it would work, as you can attach an image from a web url. Dropbox is free, and allows you to put images in it to share. The trick seems to be shrinking it down for the file size limitation. This guy below uses image shack for the resize. Maybe there is another free service (instagram maybe?) that could get you a web friendly size at a public url.
This ipad app is 3 bucks and resizes as well as shares it to dropbox: OneEdit for iPad - Batch Image Edit, Transfer & Upload for iPad on the iTunes App Store
Here's the free way though -
Intructions from whpalmer4: iPad: how to attach photo to msg? - The Omni Group Forums
Install the Dropbox app, if you haven't already done so.
Launch Dropbox, and navigate to the Public folder. Now tap the + at bottom left, and choose Existing Photo or Video. This will launch the photo picker and allow you to select an image which has been saved in your photo library. Once you've done that, the image will be uploaded to your Dropbox account and can be shared or published.
With the photo you just uploaded selected in the Dropbox sidebar (you should see the image on the right), tap the little chain link button in the menu bar, and choose Copy Link to Clipboard. Because you uploaded the image to your Public folder, this will give you a link that you can publish so anyone can see that image file.
Now leave Dropbox and launch Safari. Go to ImageShack® - Online Photo and Video Hosting
and tap the "url" button next to Upload. Then click in the "Paste image url here" field and paste in the URL that you generated earlier. Now make any changes you want to the image size, label, etc. and upload. When it is done, you'll get a list of links to share your image. I typically use the Forum Code choice. Tap in the field, tap Select All, then tap Copy (which will show up off to the right). Now you can go back to the page where you are editing your post and paste in the contents of the clipboard to insert the image on the spot.