Large templates may take time to upload and may be slow to process later on. The current official limit is 20MB. The unofficial limit for “close friends” is close to 40MB.
A better way to upload large templates
Watch a Flash demonstration or read the full help post.
The bulk size of the file is taken by images.
Replace them with simple solid-fill placeholders produced right in Corel.
The template may look too unattractive, like this one:
Upload and test the template using attractive images. When the preview is generated look for SAVE link under the image. Click on it to replace the default preview image with the current one. Now your template thumb looks OK and the file is still small: