Hmm.
I usually scan pictures from books or copy them from pdf-books then alter them in the-same with layers and combine with other sourse mat found on the internet.
lately I have been trying to 'cartoonize' the pictures before colouring and shrinking them, some have way too little contrast to make nice icons. It helps with those details that make things unclear when small too.
see, this next magic-button is a small piece of a WH roleplay warlock image:
just some green layering, some colour, the source image on overlay and some toplayer tweaking to make the detail in the button more clear.
edit: Do you still need that Old-ones monastary/temple? If so google for some inca stuff machuPiccu might work.
edit wadda ya think of this dwarvenminer?
Haven't given it any background yet or a border.
('cause I don't know the BG style. and I could zoom in on the torso to get more detail.)
edit2: Any ideas on the BG for Dwarves? brown or grey rocks could make the dwarves invisible.

a new skavenmagic button, almost from scratch: "wither" or any other curse-like spell.
ooh! and a cencerbearer.