I would advise against doubling the size of the tiles for any reason, especially if you intend on keeping some objects at their regular size like the skull.
It might seem like a small thing but it instantly destroys the universe your pixels live in to me when you break a rule so fundamental to pixels.
Other than that, there isn't much to comment on, sorry if I'm coming off harsh- it's not intended.
There isn't much deliberate detail, the dirt/cliff texture is just 3 tone noise. I think you need to focus more on the textures and detail for these objects, I feel like you're just representing the very basics of video game graphics, which on a level is kind of interesting, but I don't think that's what you're going for.
Again, apologies if I'm being too blunt.