Q: Family share just photos?

I don't know about Family Sharing and doing what you want but you can create a Shared Photo Album, set it up so that others can add to it and make comments.  Only you will be able to delete a photo from the album. 

Do all of your family use Macs?  If not you may have to create a public Shared Album and give the URL to it only to those you want to participate in it.  I'm not sure on that as I've never used a PC so have no first hand experience with them (yes, I've led a sheltered and privileged life )

No.  It's an album in the Photos Library.  To start group the photos you want to begin with and put them in an album.  Next, select all of the photos in the album and use the Share button and select iCloud Photo Sharing from the menu:

In the next window select New Shared Album.

Then fill in the album name, add the emails addresses and create.

The recipients will get an email like this:

Here are some Apple documents on shared albums:

iCloud Photo Sharing FAQ - Apple Support

My Photo Stream and iCloud Photo Sharing limits - Apple Support

When the recipients subscribe to the shared album it will appear in their Photos library under Shared:

You may be able to do what you want with Family Sharing but I am not familiar enough with it to guide you.

Mike, you can share up to 100 different shared albums with your family - so you can set up several shared albums for different purposes, one album to share vacation photos, one album for wedding photos, etc. - it is pretty flexible.

See this link:  My Photo Stream and iCloud Photo Sharing limits - Apple Support