It looks like a basic map I would've done years ago. To improve it, here are some suggestions:
1. Water doesn't run uphill
2. Avoid line-straight cliff walls, try to make them more natural with curves (not too many, exaggarating is never good either)
3. Be careful when you place shore tiles, I can already see errors in the shoreline.
4. Old C&C1 building ruins don't look too good on the rocky ground. Try not to fill an area with only one ground type, but use a combination of, for example, clear, sand and rocky.
5. Try to make the Tiberium fields less bland. You can select different Tiberium overlays from Special/Overlay -> All Overlay. Overlays TIB01-TIB12 are the green Riparius Tiberium (TIB13-TIB20 and TIB2_13-TIB2_20 are used for the slopes, be careful when placing these, because it may crash the game if done wrong), while TIB2_01-TIB2_12 are the blue Vinifera Tiberium.
6. Tiberium doesn't look good on paved road. It cannot grow there on its own, so it doesn't make sense why Tiberium should be there at all.
7. Slopes. Same with cliffs, try to make them more natural by making them less rectangular. Also, I recommend you to add more slopes/ditches around to make the terrain look less even

Now there's a few

Good luck with your map

EDIT: 600th post!!! :O
This post has been edited by Crimsonum: Feb 27 2010, 07:51 AM