its possible with scripting
lets see, this would take some time to do, but hey
NPC Code:
// NPC made by screen_name
if (created) {
this.x=0;
this.y=0;
timeout=.05; }
if (timeout) {
if (this.x<64) {
if (tiles[this.x,this.y]==9) {
putnpc treeimage,text,this.x-1,this.y; }
this.x++; } else if (this.x==64) {
if (tiles[this.x,this.y]==9) {
putnpc treeimage,text,this.x-1,this.y; }
this.y++;
this.x=0; }
timeout=.05; }
this would test for the tile of the top corner or a tree and put the tree top image on the one to the left of it
this would take some time though :S