Quite a fruitful session before work; tweaked a few values here and there to cope with certain things starting at 0 and others at 1 (for instance, you define a 10x10 array as 10,10 but index it using 0-9... seems obvious, but nobody told me!). Added the ability to 'store' different tiles in the Left and Right mouse buttons, then added a tilestrip at the bottom of the editor, got it scrolling using keypresses, and allowed the user to choose their Left/Right tile by clicking on the tilestrip. Also had to expand the current tileset to hold 256 tiles (and fix more nasty indexing problems... grrr...).
Admittedly, none of this is exactly rocket science to the average coder, but I'm having a lot of fun coding again, getting results, and working through bugs. And considering I've only officially been using the package since Friday, I'm pretty pleased with my results.
