This post cracked me up because it reminded me of an old Rosanne episode where the power is off and everyone is sitting around bored. D.J. tries to entertain everyone with a story that he made up as he went along. You seem to be struggling like him.
Basically, you dont have a story you have a vision of some shots in your head . There is nothing wrong with that. I assume you are being graded on your 3D skills not the story you choose. Besides, many movies are based on the action in the movie and not necessarily the content.
How about this. The guy comes home and finds the house a wreck. As he walks around the house he finds what looks to be damage from an enormous dog. The sofa has bites taken out of it. Pillows have been shredded. In the kitchen the fridge has been raided and food and wrappers are all over the floor. Maybe he even finds the cat all tied up and gagged. Paw prints everywhere, even the ceiling. The bathroom of course has all the toilet paper off the roll, and a big puddle around it like the dog has been drinking the blue water. Maybe the soap has a big bite out of it.
When he finally gets to the dog it turns out to be a tiny, adorable puppy. He puts a leash on it, to take it for a walk and the story ends with him being dragged out the front door.
If that one doesnt inspire you how about something about?:
Do something with an alien in the house.
He is late for school/work and cant seem to get anything done quickly because nothing is cooperating. Maybe he tries to tie his shoes too fast and breaks the string. He put his socks over his shoes or under wear over his pants. He tries to shower too fast and forgets to wait for the water to warm up and you hear him screaming from the cold. Then he trips on the shower curtain as he exits the shower. The toothpaste squirts on the mirror because he squeezes it too hard. He is making toast and scrambling eggs at the same time (note his hand is on frying pan). The toast pops up, he reaches with other hand, but it is still hot, he throws it up in the air. He sees the toast is about to hit him in the head, and his natural reflex is to shield his noggin, which he protects with the frying pan (bonk!!!) hes out cold and the story ends.
Keep trying. Maybe the suggestions you guys get will get your brainstorming.