You should be aware at first that there are different Creative Commons licenses. Many of them, in fact, don't allow content usage for commercial purposes (what publishing on Steemit is).

Therefore it's very important under which CC License a photo is available and what we are able to do with it. As, in an example, some licenses don't allow creating derivative work or there might be some other restrictions.

As well, no matter what the site (where from we take the photo) says in general, it's important to know what the license for the particular photo demands, as most of Creative Commons licenses, in fact, demand attribution.

Here are some of the main Creative Commons licenses listed.
Here are some different licensing types.

Here are some examples of different licenses (and that are just a few examples):

• CC0
• Attribution 4.0 International (CC BY 4.0) - Full license legal code
• Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) - Full license legal code

There could be many other variations, therefore, it would be very wrong to assume that in general "the Creative Commons license don’t require you to source back to them," as it's simply not true.
It entirely depends from one license to another.

As well, here is a good guide how the attribution should look like when it's needed.

• Best practices for attribution