While technically you don't need to list a source for CC0 images (like those from pixabay) there are some on steemit that want to see it so they know the image really is CC0. CC0 means it's free to use including for commercial use which your blog posts on Steemit are commercial (you get paid). At the end of the post it's really easy to just put a line that says Image Source: (list your source) or do it under the image.
Anyways @insight-out was asking about the image as she featured you into the contest which will bring you traffic we want to know you have all original content and your photos are either yours or legally allowed to be used by you.