I think taken out of context, most of the elements kind of work... what you appear to be struggling with is the distribution of those elements, I can see there's a base line grid under all this of what, 4x4 characters? regardless of dimensions it's showing through, one of the trix with tile based mapping work is try and alleviate this as much as possible. So, rather than create just 1 or 2 tiles with a splash of flowers in, and another 1 or 2 tiles with a of grass tufts in... mix it up more... it'll help...
I like the fact you've gone for the flat plain background approach... this is how I've done BG's in the past, and it's similar in styling to the classic zelda series (in 2d).
A few more pointers...
- try to dissapate the lines of the cliffs they turn vertical and peter off into the main green mass, currently it's very stiff the way they end.... try a few tile variations too just to mix it up.
- where the cliffs meet the grass at their bottom, try bringing tufts of grass over the front of this to try and push the cliffs into the ground and make it more homogenous... currently they're flring over the surface and are totally disconnected.
- the dirt in the path is a little repetetive... try varying the size (and distribution) of the texture pattern you've got going on... currently is the same 2x2 pixel block, rotated and placed in a random fashion... try making 2 or 3 variants of this basic block, say, 3x3 pixels, and 1x1 pixels, and then redistributing them across you're tiles.
- the tree's a quite nice, but the feel like they're falling backwards, try stacking those layers of leafs a bit more, giving a sense of overlap to the layer below it until you reach the top.
- the flowers are nice and simple... but again you can push this a bit more by creating some variance in the distribution, scale and color too...
General rule of thumb I find when creating this kind of stylized art... keep things ODD... when I say that I mean... count each of the elements in the tiles, or characters and if the result is even, then add 1 or substract one... for example... you have plenty of tufts of grass in their own 8x8 pixel character tiles, one has 4 blades in it... 1 too many... the ones with 3blades work better... also, there's some flowers in a tile (red petals, whit middle) - you've got four grouped together... either add one, or take on away... don't ask me why it works it just does... its one of those magic things... keep grouped natural elements together in odds not evens...1,3,5,7,9 etc...
Read up on Tesselation.
Love the colors - makes a change from bright green grass...
keep it up...
