As I understand it (I'm still new to all this Mac/iOS stuff), if you want to create a universal iOS app you can do one of two things. You can either create the game with the highest possible resolution and then WME will downscale it on smaller screens, or you can create multiple packages, one for each device, and include them all in the app, and WME Lite will choose the package it needs depending on what device it's running on.
There seems to be advantages and disadvantages to both though. If you create one set of hi-res graphics for the iPad, then the aspect ratio for the iPhone will be slightly wrong, giving you some black bars at the side, as the iPad is 4:3 and the iPhone isn't. But, it means you only need one set of graphics. If you use multiple packages then you need to include all of them in the app which will create a larger app to download, but you can use the correct aspect ratio for each device.
That's as I understand it so far.

Presumabely with the texture size, you can simpy have two 1024 textures, and then put them side by side in the scene layer to create a 2048 scene. Not sure about that as I've not got into that yet.
