Are you serious? =) You have hundreds of options to improve your game! You have made a base and now you can develop and develop your project.
Environment:
make several types of cacti, small, slightly wider than usual, with flowers,
make a deeper and richer background. If you divide your game into levels, you can make mountains, forests, desert,
you can add a change of time of day, it will diversify the game and make it more interesting. At different times of the day, you can spice up the location with birds, bats, or squirrels in the trees. At night, you can make the area around your character glow, and give him a flashlight,
Gameplay:
you can make multiple characters, give them your perks. For example, a boy will have a x2 jump and he can decide how high to jump, a girl will have an umbrella and she will be able to soar for a while. Characters can sometimes walk like a shadow through cacti instead of jumping, throwing something at cacti and destroying them,
you can make various bonuses that are scattered on the mission,
you can make various perks for the character that are bought for points in the mission. For example, extra life, speed increase, rage for a short time and the ability to destroy cacti,
if you have several characters you can make skins for them. Let the points be saved after each mission and the player can buy someone in the store for them.
You can make your game completely black and white like cartoons of the 60s, and with the points earned the player will paint the location, opponents or buy sounds and music. You just need to make some kind of progression in the game so that you can play it many many times.