Some things to play with...
Keep in mind none of this is documented/supported, so things could change/break. It's just stuff we needed in one place or another.
Easiest way to play with things is in button labels, since you can see the results as soon as you type.
<%error> <%update> <%oned:4> <%oned:3> <%ddbi:5> <%ddbi:155>
<%tbim:rename> <%tbim:makedir> <%fdbi:8> <%fdbi:12>
<%winlogo> <%bulb:1> <%bulb:2> <%bulb:3>
<%weblink> <%windowlink> <%menulink> <%manlink>
<%bullet> <%arrow> <%arrowu> <%arrowd> <%arrowl>
<%stars:3>
<%mouse> <%mousel> <%mouser> <%mousem>
<%checkbox> <%checkbox:0> <%checkbox:2>
<nowrap> ... </nowrap> prevents new lines, especially useful if you want one of those icons at the start or end of a word.
<fixed>Hello</fixed> uses a monospace font.
<%bg:75^100^50^#0000ff^#00aa00^#ffffff^#003333^#ffffff>
Value, Total, Width, Color1, Color2, Color3 (or "no"), BackColor (or "no"), TextColor (or "no"), Gradient, Frame, Line, Value1, Value2