Can I not edit images

I am using Filmstar (obviously) and all I really want to change was the color of the background image. I want my site to be red/white/grey. So, I took the background image into photoshop and changed the yellow to red and saved it as a new image in the same folder as the original (the original file was named back-top.png and I named mine back-top2.png).

Now my problem:
when I changed the URL (path to the image) from images/back-top.png to images/back-top2.png (literally just added a 2), the image disappears entirely. All I can see is the light grey color which is the background a little lower down. I tried to save the red image to back-top.png and the yellow image comes back. I cleared my cache and hard refreshed to make sure it wasnt just the browser remembering that image.

I also tried changing the background of the slider to an image that came with the theme but again when i modified it, the image disappeared entirely.

From all of this I gather that I am not able to customize the images and must use exactly what was given to me? If there is a fix or someone knows the problem please let me know.