Thanks, bubersson. It seems that these are missing from the current character set:
EDIT: Are you sure that it should be an E with breve and not an E with caron, as wikipedia
EDIT2: Alright, then I'll do all carons
U+010C Č Latin Capital Letter C with caron
U+010D č Latin Small Letter C with caron
U+010E Ď Latin Capital Letter D with caron
U+010F ď Latin Small Letter D with caron
U+01xx Ĕ Latin Capital Letter E with caron
U+01xx ĕ Latin Small Letter E with caron
U+0147 Ň Latin Capital Letter N with caron
U+0148 ň Latin Small Letter N with caron
U+0158 Ř Latin Capital Letter R with caron
U+0159 ř Latin Small Letter R with caron
U+0164 Ť Latin Capital Letter T with caron
U+0165 ť Latin Small Letter T with caron
U+016E Ů Latin Capital Letter U with ring above
U+016F ů Latin Small Letter U with ring above
Although that's still quite a list, it shouldn't be too much of a problem to add those. Please let me know if you come across some other missing characters.
Let me also open up this offer for other Latin-based language. If you miss any special characters for your language, let me know. The overview below lists all characters we currently have. You might as well add the characters from the list above to that, because we'll have those in the near future. The list of unicode characters is available here
if you like to make a list with missing characters like the one above for your own language.
Please note that this offer is only valid for Latin-based languages, not Arabic, Cyrillic or Chinese etc. It's not that I don't want to add characters for those languages, but it's just that I'm not creating them.
EDIT3: All missing characters for the Czech language have been added and the OpenGFX font is now used when the Czech language is selected (at least, in my local version; you guys out there have to wait till alpha 5.0
The following languages still have missing characters (that is, the game switches to ttf-font mode): Afrikaans, Croatian, Esperanto, Finnish, French, Icelandic, Latvian, Lithuanian, Polish, Portugese, Romanian, Slovak, Turkish and Welsh.