Dark Mode and Corkboard

Can I keep dark mode and still use the corkboard in light mode? I want a cork-colored, cork-textured background with white lined index cards. Dark mode doesn’t seem to let me do this.

With the exception of the lines (which are made to look good on darker backgrounds, as will be typical here), yes you can choose whatever card colour you prefer in the Appearance: Index Cards: Colors preference pane. The corkboard look itself is in that same generally area, under “Corkboard”.