Source for downloading extra bitmaps?

Mac OSX Mojave 10.14, Libreoffice 6.2.5.2

Hi everyone, upon checking out the bitmaps in LO, I noticed there is only a small range; does anybody know where I might be able to download some extra bitmaps?
I want to use the bitmaps initially to designate table cells that should be ignored/not filled out.

Thanks.

Bitmaps for the gallery? What purpose are the bitmaps for? Some “extra bitmaps” (images of different specification) are part of some extensions.

For better replies EDIT your question, please.