Hi, Tho I am new to this site, I have years of experience doing this exact project for ski clubs. I do the advertising signs for their destinations and have to locate a collage of pictures for each particular trip. I have also found some sites without watermarks that I use. As 500 cities an 5 images scaled and cropped is 2500. Honestly, the time to complete this cannot be determined at this time and I am leaving that blank and hoping you can trust me with this project to be done correctly. Thank you for your time and consideration.