Here are the two different workflows I use:
PREFERRED WORKFLOW
*create the block as normal
*after creating it, copy JUST THE GRAPHICS off to one side of the drawing somewhere
*I manually assign these graphics a lineweight of 0.014"
*I plot this with the 'publish to PNG.pc3' plotter setup
*for the page size, I use 80 pixels by 80 pixels, and the settings in the screenshot 'PNG ICONS'. Basically, Portrait orientation, fit to paper, and center the plot. No plot stamp.
*once it's plotted and saved to the correct location, it's ready to be used in the Icon Menu Wizard. Don't forget to delete the unneeded graphics from the block file.
THE LAZY GUY'S WORKFLOW
*google the thing you're making a symbol for
*look at the 'images' tab
*pick one and download it
*convert to png using Irfanview or something similar
*use that instead of drawing one up
*example: the screenshot named 'motor brakes'
Pertaining to the 'preferred workflow', that lineweight that I use on the graphics is pretty arbitrary. I do that so as not to get really faint icons, like you see in the screenshot called 'faint icon'. YMMV as far as that goes.
Hope this helps,

Jim Seefeldt
Electrical Engineering Technician