From what I can see in your site, in the folder /media/helloslide/ you have 4 images:
You changed only 01.jpg and 02.jpg, I see 3 and 4 as the originals that came with the theme. Try replacing that image with one of your own.
There’s no other copy of those images in the theme, if it’s not that I really don’t know. Change that and tell me if it changed something. If not, tell me anyway and we’ll find a way to make it work.