We have done this on the ECC before, but not for the 1.7.0 release. The way we've typically done it there is to grab a clean Lucid image (emi-07EE3567 looks like it would do the trick) and install AppScale on it as follows:
and that would get your image in a state where you could bundle the image, upload it to your own bucket, and register it to get an emi from that. We've run into issues where the private DNS doesn't resolve correctly (which AppScale assumes works for the directions in the above link to work), so there's an alternate cloud deployment style, which we call "cluster over cloud", that uses cloud-based resources like a virtualized cluster. Once you get an emi from above, follow these directions (
https://github.com/AppScale/appscale/wiki/AppScale-on-Cloud-as-Cluster) and you should be good to go. Let us know how it works for you, and if you get it going and make it a public emi, we'd love to share it with the community!