The biggest thing I noticed when looking at your illustration was that some of the lines for SpongeBob's body—since it's just a box—were diverging toward a different vanishing point. The lines in red show exactly where this occurs, while the lines in blue show an example of lines correctly going toward a single vanishing point. This can be applied to the lines going down and to the right as well. You want to make it a habit of drawing through your form to check if your lines are diverging or converging toward the correct vanishing point. You can also achieve this by extending your lines further to see exactly where they land on your horizon line, or where the lines intersect. Remember, it's not about being perfect, as human error is inevitable; instead, your focus should be on believability. Overall great work!
oh!!! thank you so much! i painted this with no base sketch, so i guess i'll stop doing that, so that i can get my forms right!!!