I for one have printed off signs on thin paper, let the ink throughly dry, wet, rub off a layer ar so of paper from the back, soak with white glue and mount. Use a wallpaper roller to squeeze it into the structure. If a brick surface, push with finger nails into mortar lines. Blend wall and sign together using acrylic paints. My results have been mixed, but have gotten better. It's low cost and fairly easy to change if you're not happy with the results.