You can Select a theme based on platform version, as outlined in the Styles and Themes dev guide. Define a style in your res/values/styles.xml like this:
<style name="ThemeSelector" parent="android:Theme.Light">
...
</style>
Then in a res/values-v11/ folder, select your theme (probably Holo, if you're dark)
<style name="ThemeSelector" parent="android:Theme.Holo">
...
</style>
Then add icons to that style. For instance, here's a snippet from the styles.xml file from the HoneycombGallery sample application.
<style name="AppTheme.Dark" parent="@android:style/Theme.Holo">
...
<item name="menuIconCamera">@drawable/ic_menu_camera_holo_dark</item>
<item name="menuIconToggle">@drawable/ic_menu_toggle_holo_dark</item>
<item name="menuIconShare">@drawable/ic_menu_share_holo_dark</item>
</style>
The bottom 3 elements are all icons in the drawable directories. You'll still need at least one folder per resolution-specific set of icons, but you can combine the light & dark icons into the same folder, but you won't have to have different folders of icons for each platform version. Also, you'll need to list them as references in the values/attrs.xml file, like this:
<resources>
<declare-styleable name="AppTheme">
<attr name="listDragShadowBackground" format="reference" />
<attr name="menuIconCamera" format="reference" />
<attr name="menuIconToggle" format="reference" />
<attr name="menuIconShare" format="reference" />
</declare-styleable>
</resources>
At which point you'll be able to refer to them within your layout XML using the "?attr/NameOfYourDrawable" dereference, like this:
<item android:id="@+id/menu_camera"
android:title="@string/camera"
android:icon="?attr/menuIconCamera"
android:showAsAction="ifRoom" />
