How do I...

[PompeyLegend08]

Well, there are LOADS of tiles that have black backgrounds that look wierd with m game!

Example, the top corners of a large tree are black. My grass is green, and the black looks weird on the grass and it looks really cheap and horrible :(

What should I do?

[SpykStorm]

You should use a wonderful technique called layering. Here's a tutorial:
http://www.geocities.com/idontknowtutorial/contents.html?1048292445858

[ShadowTiger]

Indeed; those black colors aren't actually true black. They're just transparent pixels. When you paste them on the layer, they'll show up just fine. :)

GG spyk9etc

[Pielord]

You need to use things called "layers". Go to Data->Layers and type in the map number and screen number for the layer you want. You can also make them transparent.This is the way layers work:
Layer 0 is the screen that you are working on and effects link and non-flying enemies
Layer 1 affects link and non-flying enemies
Layer 2 acts like layer 1 but goes over it
Layer 3 goes over link and enemies but under flying enemies. This means that even if it's solid, link will go under it
Layer 4 acts like layer 3 but goes over it
Layer 5 goes over everything even flying enemies
Layer 6 acts like layer 5 but goes over it
So if you don't understand, to make a layer you first choose some other screen and place what you want to go on the layer.Then, on the screen your putting to layer on, put in the position of the screen with the layer on it. If tiles on the layer have transparent pixels, they will display the pixel on the layer below it. So if you place those tree tops on layer 3, then they will display the the grass that you put on layer 0 and link will walk under it like in many quests. If you don't want him to walk under it then put it on layer 1 or 2. I hope this helps.

EDIT: Dangit! Beaten...