I need isometric tiles for a strategy game I am building. I created some tiles myself, but they don't look very good, so I am hoping to find someone that can do better than me  :-)

Technical Requirements:
1. Isometric base tile size: 40x20 pixels
2. File Format: GIF (with transparency)
3. Look/Style: NO pixel art -> I prefer "smooth/botchy" style?
4. Desired Style: http://freeciv.wikia.com/wiki/Map_format
5. Other related examples (see at end of this post)
 
Tiles I need:
-6 x 16 terrain tiles (grassland, plains, dirt, sand...)
-1 Village + 1 Town + 1 City
-1 Tower + 1 Castle + 1 Fortified Castle
-1 Harbor Tile
-10 forest tiles
-10 jungle tiles
-1 Ore Site + 1 Ore Mine tile
-1 x 16 mountain tiles (or possibly a single mountain tile?)
-1 x 16 wall tiles
-4 to 5 farmland tiles
-3 lumber yard tiles
-2 ship unit tiles (transport + attack ship)
-approximately 5x7 military unit tiles (different sizes, 1 militia)

Payment & Schedule:
1. Payment via PayPal | other: ask me.
2. I pay US$50 upfront (no work necessary)
3. I then pay in 10 x $50 increments (=$500):
   10% delivered -> I transfer the first $50
   20% delivered -> I transfer another $50
   30% delivered -> I transfer another $50
   ...
   100% delivered -> I transfer the remaining amount
4. Total amount including initial payment: US$550

Legal:
1. I will give you full credit for the tiles (once/if the game is out).
2. Ask me if something is not clear.

If you are interested, please apply by posting links with samples to your artwork (preferably isometric) or email me at "contact [at] noblemaster [dot] com". I am willing to discuss higher payment amounts/legal options. Just ask. I am fully aware $550 is not much, but that's what I am able to afford. I am willing to go higher if you are really able to deliver what I am looking for.

Here are the graphics/tiles I am currently using for the game. I hope to find someone that can do a lot better than me. Please note I don't like the tiles below very much, so I really need someone that is able to improve
upon those/create something better!!! This is just to give you an idea what tiles are used for the game.

Base Tile: http://img525.imageshack.us/my.php?image=sampletile40x20tv7.gif
Current Game Screenshot: http://img262.imageshack.us/my.php?image=screenshot030lx0.jpg
Current Beach Tileset: http://img337.imageshack.us/my.php?image=seabedsheetvh2.gif
Current Grassland Tileset: http://img505.imageshack.us/my.php?image=grasslandsheetzn7.gif
Current Castle Tile: http://img116.imageshack.us/my.php?image=castle2pu8.gif