I make decals on my computer. It's a relatively easy process. You can either use white-backed decal paper to get the colors right, or, as I do, use clear-backed decals and understand that the printer assumes you're using white paper, so you need to provide a white background on the structure.
I find this works very well on brick walls, because the brick texture shows through and the sign takes on an instant weathered appearance. Here is a classic ad image I downloaded and made into a decal.
It does, however, illustrate a problem. I can't draw a straight line, much less paint a clean, straight white rectangle on a building. So, you can see the uneven white border. Learning from my mistake, I now paint the white background a bit smaller than the image, and I use image-editing software to add a dark border to the decal, to cover up my uneven paint job.
This technique also works well on real wood surfaces.
It takes an iron man to play with a toy iron horse.
Included this in my Free-moN module construction thread, but thought I'd post it here for the archives and to see how others do it:7Tw56VcI56QI'm sure there's better ways of doing it, but dang if this wasn't simple and easy! (Takes longer to watch the video than to do the dang project )
And especially since Tomkat-13 has already put together and shared a KABILLION signs for us... there's no excuse not to have some!
M.C. Fujiwara
My YouTube Channel (How-to's, Layout progress videos)
Silicon Valley Free-moN