There are multiple ways a user can validate a Image on the UI, In the below example we will see how to validate a Image on UI using sikuli and java.

Highlight an element in selenium
         /*
	 * Method for validating image in UI 
	 */

	public boolean validateImage(String path, String screenName, String imageDesc)	{

		try {
			Screen screen = new Screen();
			Pattern pattern = new Pattern(path);
			screen.wait(pattern, 8);			
			

			if (screen.exists(pattern) != null)	{
				System.out.println(screenName + " page validation", imageDesc + " validation is successful");
				return true;
			}
			else	{
				System.out.println(screenName + " page validation", imageDesc + " validation is not successful");
				return false;
			}
		} catch (Exception e) {
			e.printStackTrace();
			System.out.println("Exception in validateImage");
			return false;
		}		
	}