Great
The small letterbox is already done. You can
download it here and incorporate it into your work if you like (you don't have to mention me if you do since it is such a small modification).
For those who want to use the small letterbox a little installation guide:
1. Create a backup of the SkinDefiniton.xml you want to change.
2. Copy the content of the zip-file to folder of the skin you want to modify.
3. The original SkinDefintion.xml should now be replaced with the SkinDefinition.xml from the zip-File. Furthermore there should be a blank.tga in the root folder of the theme and two no letterbox.images (letterbox_small and letterbox_levelcap) in the panel-folder.
4. The new SkinDefintion.xml should load a small letterbox without any buttons. If you want to use the levelcap-version for your characters that have reached the levelcap, simply open the SkinDefintion.xml, look for the following line near the top
<Mapping ArtAssetID="letterbox_bottom" FileName="panel\lm_main_panel_letterbox_
small.tga"></Mapping>
and change it to
<Mapping ArtAssetID="letterbox_bottom" FileName="panel\lm_main_panel_letterbox_
levelcap.tga"></Mapping>
Keep in mind that this is not a functional change (a functional change would cause tons of complex code I don't want to bother with right now). The "experience/level progress indicator" will still exceed the letterbox, so don't use the levelcap-version on characters that are still deep in the leveling process.
@Daimon
Can you please remove the tabulators from the code (located between the ArtAssetID and the Filenames)? The modifications I like too offer contain many "search for line x and replace with line y"-instructions, and it'll be much easier to explain these instructions (or to find the lines that have to be changed) without these tabulators.
And there are two buttons (start-menu and online-help), that are located in the letterbox, but the corresponding code isn't located in the letterbox/minibuttons section in the xml-file. Can you change that to? Should help to avoid irritations among those users who aren't used to xml-code (but like to apply some modifications).
P.S.: Final question to the American players: How does LUA interfere with the themes? Do the plugins use the images of the currently active theme (e.g. panels, borders, titles etc.)?