The basic topics are always going to be there for everyone, fine tuning anatomy. It's not really worth spending much time on because it's such a widely available and covered topic in most tutorials that someone who seeks improvement will easily find and spend time on their own. I'm willing to bet you're much more interested in more nuanced and specific topics.
Seconding Eightfish, at a cusory glane the subjects feel very stiff. There's a lot of loss opportunity to show personality and dynamism, but I do notice there's attempts for it. When you build your illustrations, what's your approach? What elements are you prioritizing, like say, the anatomical structure of a figure? How are you placing your subjects in regards to their environment, what does that process look like? I'm asking because I don't want to assume what you are and aren't doing, but also hoping that these questions also might spark some thought processes that could review problem areas. I know that that's what worked for me when instructors criticized lack of energy in my drawings.
Just to pick out one drawing:
The thing that jumps out to me first, is the deer girl in the foreground is very off balance. Her center of gravity is heavily off-set making her lean too far forward, even for a leaning-standing position. Drawing a red line that passes from the center of her skull towards the floor reveals that discrepancy.
Stiffness strikes problematically again with the further most figure in the background, the (fox?) gentleman, who appears to be talking to the disinterested Hyena. His supporting leg is very straight, and the indentation where his hips bend slightly don't truly suggest he's leaning against the counter as much as almost planking it vertically. Even if a limb may be a structural support, it still has shape language that describe the muscle masses which tighten and curve as the body responds to the required positioning. Which is just a fancy way of saying: be careful in thinking that locked joints = perfectly straight limbs. Look for that subtle curvature and energy in reference models!
This last part is just nitpicking, it's more concerning a combination of writing and illustration in reference to character's body language. People talk about "Drawing with symbols" right? Like we know the difference between a "true" nose, and a triangle drawn on a face to represent a nose, rather than actually draw a true one. When it comes to body language, I've found that there's "true" and "symbol" language as well. What gets defined as symbols vs 'true', is when in our minds we automatically defer to the easiest answer, not necessarily the 'truest' or even the 'most interesting' for our specific characters.
We know that everyone has very unique personalities, and we also know that body language makes up some 80%-90% of our communication. Therefore, when someone is speaking, they should not be using the exact same hand and bodily gestures as each other, let alone a majority of characters that ever get drawn, ever. This is a long winded way of saying watch out for Mr. Fox's hand gesture, because I've seen that exact same pose across thousands of illustrations. Holding a single hand up, palm facing upwards with a mouth open to suggest conversation is effectively a 'symbol' - or placeholder gesture to represent someone is engaged in conversation. Because of it's sheer over-usage, it's not an effective one that really says anything interesting about the illustration at hand. Let alone what the characters themselves may be really thinking or feeling at that given point in time.
For example I was watching a Judiciary committee and one man stood out to me as he was talking, because unlike anyone else in the room, when he was saying something affirmative he would nod over and over, and also blink! A lot! It was a very interesting quirk. Something like this - while being hard to show in a still image - is an example of "true" body language to character. All I mean to say is, observing people more closely will help you build up a solid reference library of specific language that illustrates an effective and interesting story, rather than a vague or general one because the brain is defaulting to the most common denominator for the kind of interaction you're drawing.
I know it's something that's not going to be a huge factor for a fanart, but it might help with personal work.