I'm not aware of a pre-built AMI with SY, but have you seen our integration with OpenShift? OpenShift apps are backed by EC2, so you indirectly get a precofingured SY environment on Amazon. :-)
Here's the OpenShift site if you haven't seen it already:
After you create an app with the EAP 6 cartridge, you'll notice that SwitchYard is available as an optional add-on cartridge. This will add the SY modules to the EAP instance in your OS app. Only thing left to do after that is update the standalone.xml used by the server to include the SY subsystem. One way to do that is to follow something like this:
That said, we are looking to update our tooling to remove messing with the standalone.xml on your own and have the tooling do everything for you automatically. You can follow that work here:
Yes am aware of OpenShift. It looks VERY good! The only reason we are not going with OpenShift is there is still no paid, and large capacity, tier. There is advertised pricing, but the top tier is still not launched.
Our app is rather resource hungry and does not run on the free tier.