Looks like you didn't set the tile size correctly.
Check Map -> Map Properties and there look for tile size. Does this size correspond with the size of the tile in the image? If not, change it. It seems like it's too small, ie map's grid size looks as if it's using the default 32x32 but your tile image looks like it's 256x256 (guessing).
Are you using "Collection of Images" Tileset? If not, you'll also have to set the tilesize correctly in the New Tileset dialog:
I believe you can't change this after the fact, except when you manually edit the TMX file with a text editor (close Tiled before you do).