With the latest 4.2 update, you can now import/export data into/from the "Send Photo Later" queue. This is great for backing up the queue, or if you need to re-upload photos.
To access this new feature, go to Settings and select "Send Photo Later", and note the new import and export buttons.
The import feature will import any of the tab-delimited files generated by Sparkbooth. If you have the prompts enabled, you can import the sparkbooth-prompts.txt. If you have uploads enabled, you can import the sparkbooth-uploads.txt file.
If you want to import the prompts or upload log from another computer, copy the photos folder over and set it as the layout folder under Settings > Saving before importing the log file.