I've been thinking of extending the keyboard layout for a while to include a few characters I want to type in my future stuff, so I gave yours a try and found a bump
In the attachment you'll find your normal keyboard plus upper-case accented letters, cent and yen signs, Icelandic thorns, etc. Pretty straightforward to add in theory. Now for the strange part:
When the keyboard appears, you can type the cent sign "¢", and also "¶", "§", "µ", "þ", letters with diacritics, etc. without problems. Then, pressing shift or CapsLock brings up the "upper case" labels on the keys, but only "¥" (I put this as Shift + ¢) can be typed correctly -- the letters with diacritics are all converted to lower case (i.e. you push "Æ" or "Á" but get "æ" or "á" instead, etc.)! Why?
On a different note, I tried to use text labels for the arrows but the font used to draw the keyboard lacks those glyphs. I've tried to edit your PNG files to make the up and down arrows fit in the "keys" but all I get are black blobs. Any comments on this?
Thank you for another impressive piece of work BTW.