I think you're off to a good start on this. Many of the issues are common mistakes that will work themselves out as you draw more and more, so long as you push yourself.
The first thing that jumps out at me is the shading and color palette. Right now you have one major light source and one minor light source and you do shade largely within how those would send light out (with some issues with the light intensity of the areas hit versus those not), the problem lies in the actual colors you've chosen to represent the light casted. Right now everything is lit in a way that suggests a very clinical white light when in actuality the fire would cast much more intense orange-ish warm glow that would show much more, especially on that robot dude and the guy with the white and red shirt. Also the the darker areas on the characters and logs could be made much darker to push the contrast. This lighting would also apply to the grass, if you observe grass at night around a campfire it really doesn't look too green at all, it takes on oranges and browns much more prominently. As for the areas that the fire doesn't hit make those all cooler colors and darker, try using blues, greens and violets to push the contrast that the oranges from the fire would create (something that is already going on a bit here, just expand on it). Fixing up the lighting will help to sell the atmosphere of the drawing as well as push the contrast and intensity of the piece.
The poses of the characters are all a bit stiff, I think the best two are the girl and the dude in the middle but there is still room for improvement there. Look into the line of motion concept for poses in order to get more personality communicated in your poses also doing some studies of sitting figures will help in communicating the depth and volume of your characters sitting down. Drawing people sitting - especially on abnormal surfaces - is very tricky and I think you're off to a good start here.
Your linework is a bit wobbly, you can do a few things to fix that, the first and best (in my opinion) is to be more confident in your strokes, do them faster and use your shoulder as opposed to wrist or elbow to do the motion, this method is in general a good thing to get comfortable with if you aren't already since it will help you not only get better lines, but also keep you from getting carpal tunnel.
As for the composition, this is a bit vanilla, standard sort of shot that you see a lot, not that there is anything wrong with that, but if you want more drama in your pieces try playing with camera angles.It does create more obstacles to overcome in terms of foreshortening and depth of field, but the results are much more interesting to look at. Simple things like lowering the camera bit and tilting it up so we're looking up at these people even slightly can go a long way in making the whole scene much more dramatic and ominous.
Also as a side thing: from what I understand Don't Starve has an art style that utilizes very clear color palettes in each level or stage or whatever, I think if you were to emulate the game's color choices more closely, or try to use color in ways that it does, you'd have a much more successful piece of fan art and maybe step a bit outside your comfort zone, which is always good.
Anyway, you're on a good track taking on full scenes such as this, just keep pushing your art and you'll be A-Okay.