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    From what I can see in your site, in the folder /media/helloslide/ you have 4 images:
    # 01.jpg
    # 02.jpg
    # 03.jpg
    # 04.jpg
    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.