The only way I could think of is going in the Community CSS and putting

.theme-fandomdesktop-light .dark-mode {
    display: none;
}

.theme-fandomdesktop-dark .light-mode {
    display: none;
}

Then where you want the images to switch depending on light/dark mode you could put

[[File:FILENAME|class=light-mode]]

For light mode and

[[File:FILENAME|class=dark-mode]]

For dark mode