Themes are an aesthetic part of Leap Day. Each level will be assigned a theme, with a corresponding background and platform aesthetics. Themes are not selected randomly, but instead follow a specific order. They do not influence level generation nor the various components of a level, as those are always dependant of the level seed. There are currently ten levels which are cycled through for every level. Furthermore, the "Tomorrow on Leap Day" room which appears at the beginning of every level will display a preview of the theme selected for the next day. Each theme has two distinct platform types which are used throughout the level. Smaller platforms however have default textures which are shared throughout all themes.
A medieval theme with mainly red and dark purple colours. The background is mostly composed of floating castles and giant vines. These elements are surrounded in clouds, and dead leaves can be seen falling.
A gothic theme with dark and gloomy colourations. Many floating islands compose the background, decorated with purple trees and iron fences. Large intertwined tree roots are coming out of the sides and from the bottom of these islands. Behind, large wireframes and pointy hills can be seen. This theme has a stormy weather, with a constant rain covering the screen and occasional thunder.
This theme is mainly turquoise, with shades of light green and blue. It mainly consists of a wide waterfall in the center, with some cliffs on either sides. Some large mossy beams will occasionally cross the gap between the two sides. Groups of purple mushrooms are sprouting on the rock faces, and some fishes can be seen in the water stream.
This theme is set in a lush green environment. Most of the background is composed of foliage and tree trucks. Some leaves can appear on the sides with apples on them, and occasional fireflies will be flying across the screen.
A volcanic theme with dark red and purple tones. The center of the screen is occupied by a large red volcano which will constantly emit dark smoke clouds. The sides are made of piles of skulls and bones. Most of these seem to belong to some enemies in the game or some characters seen in the starting room of each level. Some large chains will go across the screen, and some fire particles will be floating in the air.
This theme has a dusty setting. The center of the theme has a large sun that is setting in the horizon. Around the sun, a silhouette of a pyramid can be seen, alongside vast sand dunes. There are multiple cacti set on platforms. Dusty wind blows continually across the screen.
A modern theme showing a skyscraper under construction. Characters from the audience in the beginning of each level can be seen in the background working. A helicopter flies around and holds the words "Leap Day 24".