the main thing it looks like you need to work on is volume. you aren't just drawing 2d shapes, you're drawing 2d shapes that you have to fool the viewer into thinking are fully 3-dimensional. you have the beginnings of texture on the thighs/arms/back - continue that! texture is perfect for faking volume. the ears and hair are the best portions of the img in that regard, you rendered depth well on those.

your biggest mistake on this one is the shading on the body. it's very soft and airbrushy, with almost no variation. going back to the hair, you have a combo of hard shading and a gradient that, when combined (even if it's not realistic!), achieves exactly what's needed. good combo of it on the tail too, especially the bit that's directly behind the body. you have to continue that with the rest of it. remember that muscles and dimples are also a thing, and while you don't have to render every single ligament DBZ-style, a soft shadow or two in the right places will work wonders. texture helps here too, because as-is your figure's legs and arms are very flat.

when going lineless, you have to consider your silhouette much more carefully. if your char's hands are outside the body in the negative space, make sure you spread the fingers out some. they don't all have to be splayed, but right now it looks like your char is wearing mittens. while i can see some veeeeery light shading between the fingers, it's not enough of an indicator that those are individual shapes. same with the feet.

i'm gonna come back to the tail because it's well done, but you did the thing that not a lot of furry artists do, which is remembering that it's an extension of the spine and doesn't just sprout from the ass cheeks. that lil bump on the inside of the bend? A+. fantastic way of showing weight. do that with your feet, pls. they hold up the entire figure, not just the tail, so they need to have that same sort of oomph. at this point, even if you put some shadows underneath the feet to show your char is standing there, it won't work because the feeling of that weight will be missing. he'll just be floating in the air with some shadows below.

one more important thing, also: facial features and foreshortening. they're the same thing. right now, you kind of have it, but you're not sure. if you take a look at the eyes, the back eye is curving away from us, but the front eye is basically a straight line. they're also the same size. always remember that the head is curved. don't exaggerate it, you're not drawing humpty dumpty or anything, but that curve is so so important to the face, otherwise you'll always have that subtle off look. the eye (or other feature) that's further away will always be smaller. not by much. just enough that along with the curve it shows the face is turned away.

small detail: always make sure your pupils are pointed in the same direction. if one is slightly lower than the other, you'll wind up with a walleyed look. if that's your intention, cool! if not, double check.

back to the foreshortening bit: your char's back arm is pointing straight down and straight out. the face is turned toward the viewer. the hand is holding a bottle to the mouth, so the hand must be in front of the face. but the arm is in strict profile view. solution? it's ok to not show the entire arm or hand or even bottle. tilt it. the upper arm can stay the same, but the forearm needs to rotate at the elbow. a 3/4 view would be fine. this way you still have the arm, hand, bottle, etc visible, but you're also not breaking anything that doesn't need to be broken (like his wrist and/or elbow).

the pose itself can probably be solved by getting up and doing it yourself. if you have a mirror, that's perfect, but you don't need a mirror to feel it. when you lean forward like that, your shoulders move forward too. if you're moving one shoulder up, the other must stay down. the way you got it now, both are pulled back. i tried that pose myself just now, and if you try it you'll see why holding a bottle to your mouth that far away from you won't work unless your forearm is 2x as long as your upper arm.

a really quick example of what i mean:



i'm a little confused on the balloon/the action happening with the tail, but here goes! from that bend in the tail , it looks like it's not moving. if the tail is still, the balloon should also be still. if the tail is moving, which is what it looks like you meant to render w/ that string, then the balloon shape needs to reflect that. if you've ever heard of squash and stretch, it's not just a useful animation thing. light things like balloons, especially in a more cartoony style like you've got going, will change shape when moving. even slowly. balloons are also only perfectly round if they're those flat round ones you buy in stores with the fancy-ass half oxygen half regular air (because oxygen is expensive) filling, the regular ones like it looks like you got there will be closer to an upside down egg shape. they also pull the string tight, so it won't have a curve like that. a straight line indicates tension, which is what would be happening if the tail was moving and pulling the balloon after it.

edit: little details like uneven fingers will do wonders putting more life into your drawings. stiff fingers/arms/legs/tail/ears/whatev make it look like a statue. you did it on the ears, just extend it to the other limbs! note how in the crappy redline i did, the pinky is resting a liiiiitle higher than the other fingers, on the main body of the bottle instead of the neck. it's little stuff like that which gives that more natural feel.