When using images make sure that you abide by the copyright license of those images.
If possible use your own images on your poster. These images could be graphs/charts to present your results, photographs of procedures or photographs of equipment.
Infographics can be used to present information in a visually pleasing way.
Any images used on a poster should be in PNG, GIF, JPEG or TIF formats as these are better for resizing without losing clarity. These images should have a resolution of 200 dots per inch (dpi) or 80 dots per centimetre so that the quality of the image isn't lost when enlarged.
Always use the original image when adding it to your poster -- don't copy and paste images from Word.