While I agree with the tileset being a little less than exciting (I agree with the others, look at game tilesets you find interesting and see what you like about it), the differing styles of the character and the tiles are most jarring to me. I assume you were going for a separation between character and interacting tiles but it's so far detached that it feels like a completely different style. It probably has to do with the sharp maroon/brownish border that is far more saturated than everything else while all the rest of the colors are far less saturated.

Couple things to demonstrate why it's laying out weird:


This is a quick (super quick, my lines are awful) idea of the lines each of your shapes are implying as far as perspective goes. See how some of the shapes just don't adhere to the same line of sight? Your center island is definitely a point of contention here when it comes to perspective because it's sitting more flat instead of at the angle that the first petal sits.


(stars, because it's in spaaaace!  )
Another way to look at it is to shrink it down and toss it on a sphere because technically that's what you're trying to imply for your land mass, I used HarvyDentMustDie's version to contrast and give you an idea of how it adheres to the perspective.

I hope this helps to illustrate the idea a little better, sorry some of it is a bit off!

For some reason I miss the offwhite paper color from the sword and the lettering but I I understand the better fit of the white here and overall those details really livened up the piece!

Perhaps the shadow portion of the chainmail on his right leg could probably use a little tweaking, something about it feels too dark, maybe it's just the inner edge contrasting hard with it.

I need to spend some time and study your metals wolf, they always seem to pop right out.

"Let's call it a draw!"
The orange & red still bother me, instead of drawing your eye to the focal point it ends up pulling your attention to those red lines.

When you say poster I assume you mean like a screenprinted concert poster, maybe you could really desaturate or soften the red/orange to match that sort of style? I'm at work at the moment or I'd toss an edit but this is the kind of thing I was thinking of:
http://images.cdn.bigcartel.com/bigcartel/product_images/96879127/max_h-1000+max_w-1000/Marmozets_Screenadelica_Poster.jpg

Looking at this and all those posters really makes me want to do something screenprinted like that!

We're definitely overthinking it but maybe if it's a natural spring there should be a bit more of a pool attached to to the stream at the top, or maybe make the stream end hidden so it's implied?

Don't forget to widen your river a bit at the end. I was googling a few river mouth pictures and I found some cool references:
http://upload.wikimedia.org/wikipedia/commons/9/91/Klamath_River_mouth_aerial_view.jpg
http://3.bp.blogspot.com/-XnHHipZv1gk/T3gyWnNVR6I/AAAAAAAAAwA/6JXHoKp44ZA/s1600/river_Mouth+3.jpg
http://4.bp.blogspot.com/_erApd0WcEIk/TUVtyNjekQI/AAAAAAAAABs/iwgY_Oe1hxg/s1600/AQCA090%255B1%255D.jpg

Also makes me think as you get in a little more you could add some better beach area around the mouth and maybe even a little sandbar. Another idea could be to add a little hill depth around the river and really make it stand out.

Look at this reference how the mountains kinda pull into the river and define it:
http://www.flyinn.co.nz/wp-content/uploads/2011/12/Kaipo-River-Mouth.-North-of-Mildord-Sound-West-Coast.-Bob-and-June.-Feb-09.jpg

That makes me think, don't forget to use lots references of real life areas, that kind of thing always gets me really excited and launches me a ton of new ideas (as you see above)