SCHERMO, su che dimensioni lavorare:
http://developer.android.com/guide/practices/screens_support.html

As you design your UI for different screen sizes, you’ll discover that each design requires a minimum amount of space. So, each generalized screen size above has an associated minimum resolution that’s defined by the system. These minimum sizes are in “dp” units—the same units you should use when defining your layouts—which allows the system to avoid worrying about changes in screen density.

• xlarge screens are at least 960dp x 720dp
• large screens are at least 640dp x 480dp
• normal screens are at least 470dp x 320dp
• small screens are at least 426dp x 320dp

Quindi, da  portrait 320×480 a lanscape 1024x 768px  (dimensione IPAD, circa 10”)
ICONE & SPLASHSCREEN:
drawable >>  icon.png 96 × 96 RGB (con alfa)
drawable-hdpi >> icon.png  72 × 72 RGB (con alfa)
drawable-land-hdpi >> screen.png 800 × 480 RGB (non alfa)
drawable-land-ldpi >> screen.png  320 × 200 (non alfa)
drawable-land-mdpi >> screen.png 480 × 320 (non alfa)
drawable-land-xhdpi >> screen.png 1280 × 720 (non alfa)
drawable-ldpi >> icon.png 36 × 36 (con alfa)
drawable-mdpi >> icon.png 48 × 48 (con alfa)
drawable-port-hdpi >> screen.png 480 × 800 (non alfa)
drawable-port-ldpi >> screen.png 200 × 320 (non alfa)
drawable-port-mdpi >> screen.png 320 × 480 (non alfa)
drawable-port-xhdpi >> screen.png 720 × 1280 (non alfa)
drawable-xhdpi >> icon.png 96 × 96 (con alfa)
tutti i formati: https://github.com/phonegap/phonegap/wiki/App-Splash-Screen-Sizes

Risorse grafiche:

Framework: http://demos.jquerymobile.com/1.4.5/
Libreria di icone: https://fortawesome.github.io/Font-Awesome/
Font: https://www.fontsquirrel.com/

Risorse per lo Store:

Icone, immagine in primo piano e screenshot:
https://support.google.com/googleplay/android-developer/answer/1078870?hl=it