Have you noticed that Nokia just announced some great new Asha Platform 1.0 501 devices with great smartphone capabilities for developers to utilize: http://www.developer.nokia.com/Develop/asha/
From Nokia Store Publishing point of view these devices do have different size 240*320 screenshots and one mandatory banner 120*60. These things are there to ensure the richest possible Nokia Store experience for the end users. Optional fourth and fifth screenshots are also possible only with Asha Platform. Screenshots are automatically created from the default square screenshot, but to optimize the user experience you should add the right ratio scaled screenshot. See more detailed information from here: http://support.publish.nokia.com/?p=9&type=alert
Those pictures will become mandatory after you select the Asha Platform 501 devices in the distribution of your content.
And of course the JAR size limit has now increased from 2MB to 5MB with these devices. There is also more RAM/heap memory for running your fancy stuff.
Publish Support team