Hi Christine and welcome to our community
Even in traditional WebHelp output, these are simple images.
I just created a non-skinned output to check. I'm using X5 and in
this version you should be able to find the following images:
* Closed book should be: whd_toc1.gif
* Open book should be: whd_toc2.gif
* Page should be: whd_toc3.gif
So if you want to influence changes to these, you would find
them in your output folder and simply replace (using the same file
name) with the image(s) of your choice.
Cheers... Rick