Another way is to use a layer and place your image as a layer instead of as ground. Then you can have tile and movement dimensions anything you want. I don't suggest that you try to make the tile or movement dimensions match the size of your graphic, as the engine seems to think that something's wrong. I suggest that you know how large you want your map to be, and make your image slightly smaller so that the engine will read it right. You can use access to block off the perimeter of your map.
As I see it, the problem with using a PICT file as the background is that you can't have the Player move behind anything. I happen to like the 3D look when the Player moves under trees and behind houses. You CAN, however, mix that in.
Once in a while, I do use a larger graphic as a picture. But, so far, I've blocked it off so that the Player sees it but doesn't walk on it. I place it as a layer. I'm also planning on using a large picture behind images wherein I don't block it off. That means, though, that I can't use the ground tiles, but I could still use the ground tiles in the layer mode.
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-- Debra
Danillitphil Productions