The folder names need to be :
- /drawable-ldpi For low density screens
- /drawable-mdpi For medium density screens
- /drawable-hdpi For high resolution screens
- /drawable-xhdpi For extra high resolution screens
/drawable should be reserved for assets that you either (1) don’t care about which device or for (2) xml drawable assets
Then on top of that you can provide different resources based on configuration by using config qualifiers, you can read all about it here http://developer.android.com/guide/topics/resources/providing-resources.html
for instance, you can have high resolution assets for landscape with a folder
- /drawable-land-hdpi
Hope that helps