Although I do think Witter's UI could be improved while using only built-in/themeable widgets, your mockup looks very slick. If future versions were to be based on that, it looks like it would have no real problems with themes. Obviously your custom graphics wouldn't be themeable, but it would work just fine nonetheless, since all elements are custom. That's all I was trying to convey earlier: if an app is going to use some custom graphics (beyond icons), it's best to use only custom graphics. Otherwise, some parts will change based on the theme while others remain static, inevitably leading to ugliness and/or usability issues.

As someone who makes themes, I obviously like apps to be themeable. At the same time I think the fully non-standard/unthemeable graphics wazd made for AlmostTI look fantastic, and work far better than the default widgets would for that app.

It's awesome that you're offering to help improve UIs for free, but as others have said, it's important to consider when and where it's really appropriate to use custom graphics. Some apps just wouldn't work as well with the default widgets, but IMO such apps are pretty rare. And obviously, there are plenty of ways to improve a UI aside from replacing graphics.

You obviously have design skills and a desire to make Maemo look nicer; have you considered making themes? (Not to suggest that you shouldn't keep trying to help out with specific apps.)