As an experienced maper I can help you with my advises:
1 The first thing - try to make/collect custom seamless tiles - you need 3-4 tile for each type of surface
2 The second thing to make a rough and simple map based on distance, scales, sizes and locations of objects points(it can be scaled to player size(32*32 = 1m².)
3 Prepare sprites and images for all non-standard objects - benches, lamps, trees, hedges(PNG). And Prepare sounds for it(OGG 96kbps).
4 Try to do most hard work with map - use all tiles for create detailed map, do not forget to use a tools like blending and rotate tiles - it help you to create seamless surfaces with 3-4 tiles.
5 Set, scale, rotate all sprites and images on map.
Dont forget about using shading and shadow sprites.
6 If your map is smaller than 100*100 then set lights entities.
7 Сreate mapexport image (1:1) and check pathfinding tool for compare numbers of tiles for CT and T to reach way to target zones. Compare original map with yours and fix last marks. Set sounds at your map.
8 Write map.txt with all descriptions and texts as you want .
9 Create server transfer.list.
10 Create zip archive with all files, which need for play it. (Including transfer.list)
11 Create some screenshots of best places of your map and upload it and mapexport image at image hosting.
12 Only then you can upload your map at File Archive.