Heat the olive oil in a large skillet over medium-high heat. Add the onion, peppers, and sausage to the skillet and cook until the onions soften, about 5-7 minutes. (If you're using fresh celery, add it in this step.)
Add the garlic and celery seed and cook until fragrant, about another minute.
Add the crushed tomatoes and 1 teaspoon of cajun seasoning. Stir well. Reduce the heat to medium-low, stirring often, and cook for another 5 minutes or until the mixture thickens.
Add the shrimp, okra, and cauliflower rice. Stir well and cook for another 5 minutes or so until the shrimp is fully cooked (pink with white flesh). Remove from the heat.
Continue stirring and season with additional cajun seasoning, salt, and pepper, if desired.