Importing large images
The maximum size of an image that can be imported into SketchUp is 1024 pixels wide by 1024 pixels high. SketchUp will automatically downsize files larger than the 1024 pixels by 1024 pixels using a medium quality sampling mechanism. For better quality results, downsize a larger image before import into SketchUp using a photo editing program like Adobe Photoshop (one that supports bicubic resampling) and save the file as a high-quality JPEG file.
Additionally, crop any images to include only the portion of the image to be used if the image will be used as a texture in SketchUp (to minimize impact on file size in SketchUp).