RWB, I got the current sensor board you have.
PROGMEM will allow us to store bitmap arrays in external flash saving on the limited internal flash and RAM. As for custom fonts, once you’ve uploaded those to the digole, there is no need to have them in your code.
The upload is very straight forward. Look over the u8glib fonts here. The sketch I have uploads these to the digole:
u8blib_font_5x7 , u8g_font_7x13B and u8g_font_04b_03br
The 5x7 is a bit different than the built-in 6, the second is the mid-sized one and the third is small and nice to look at. If you want to point out up to 4 fonts you would like, as long as each is < 4KB in size then I can prep the sketch for you and post it.
Designing graphics is really 'touchy feely" and I often find that something that looks good on paper dosen’t always look good on the display. I added some geometric primitives to the library timb will be posting. One thing you can do is put up a basic analog panel meter (with a needle). I have a simple demo for that. With a little work and imagination, who knows what you can do!