Some of my photos don't show up in the chooser
Folia can only see photos that are marked as Public, so it is possible that you might have some photos marked as for Friends or Family only.
You can check this by viewing the photo page on Flickr and scrolling down to the bottom right of the page – there should be a section called Owner Settings. Under this heading, it should display the words Anyone can see this photo.
To change this setting: click the (edit) link and a box will appear. Select the Anyone (public) option and click the Save button. Return to folia and the chooser should now be displaying the photo.
To change this as a default for all your photos, see the instructions in the The Finder isn’t finding any of my flickr photos help article.