This is a nice start.
What are you looking for a critique on?
The first thing I would suggest is the texture and material map for the “head”. The material map is stretched and does not lend itself to appear very asteroid-like.
I’m not sure what you are using as an Earth image, but the one you have is not very good. I would do a quick Google search and get something in a higher resolution.
Those are the first two things that stick out.
To expand on what tc2466 said. The head texture needs to have its tiling adjusted. if you have UV mapped it, you may be able to scale the UVs to get a little more of the rock to show in an undistorted state, if its just a simple image texture material. increase your X tiling a few steps and see if it looks more stone like.
Your choice of background image takes the most away from the composition. As well as the portrate view. you might try adjusting your camera to give more of a landscape view. Google NASA star photos, they have some very nice high resolution deep space images posted online. Your earth isnt that bad, the blue glow could use a little toning down, but other than that its fine really, for a view from that distance.
your lighting looks pretty good for the angle of the statue and the lighting in your earth photo. remember that in space. there is only one light source that counts, and it casts pretty harsh/crisp shadows. it might help realism a bit to give the statue a bit of a turn to show off those harsh shadows. and place a light blue low intensity light behind it as a fill light (to show the light reflecting off the planet.)
Keep at it. this could be a pretty cool piece with a little more work!
your use of the title “easter island” for a space picture reminds me of a particularly memorable passage in a futurology book i once read. if i remember rightly it was stephen baxter’s “deep future” . the image here has problems, other than those already mentioned consider finding a higher resolution background image to place on what i assume was the inside of a huge sphere surrounding the objects in your scene. some of these are ridiculously big (70 megabyte jpegs) but
might help. your glow on the earth isn’t too bad though the atmosphere is far too thick, compare the 100km thick layer of air we breathe to the 6378km radius of earth. i also notice your use of chromatic aberration on the bottom of your statue/asteroid in the second image, this could be used well but in an image this simple it won’t make any difference to photorealism until other things are changed. one last thing to suggest: remember, in space there is no down. the head doesn’t have to align so closely with earth and it may be a more interesting composition if it didn’t align.