Now cute! And love the idea of a 3 x 3 grid!!! I would be fine with just the canvas and no frames. I think they would pop on the wall more being right next to it without a frame changing that effect.

Good soil + strawberries and herbs + pig face + myoporum purpureum + succulent/cacti + paint a beautiful colour (with excellent surface preparation). All and any of those will take interesting but ordinary, which you currently have, to gorgeous and eyecatching. Go for it! May the force be with you! ;-)

A lot of garages get converted into living spaces without any significant drama's and meet all building codes and standards. If the existing concrete slab floor is lower than the existing floor it get's raised up by either a new slab over a plastic membrane or in some cases if it set's set low enough, bearers and joists on piers with a new floor to match the existing. Must allow space for termite inspection. Walls are infilled between engaged piers with (usually) 70mm timber frames. These have sarking and insulation just like a brick veneer wall. Plasterboard over the top again like a normal brick veneer wall. Special consideration to termite control but again no issue. There are no cheap fixes but I've read about the spray on type's of waterproof and suchlike. These are equally as expensive as anything else. Depends on your exact situation and what you're wanting to achieve.

Looks good. Before I read through discussion, I had these thoughts. You could look at painting on the front of the wall only, not in the porch/entranceway area underneath, double strength of main colour. So you could as an option get a test pot of Dulux double Self Destruct or even triple. I would not use Monument, or similar to the roof color as it will disappear into the roof. I also think the front fence would look better painted a stronger colour from your existing but as it seems it has just been painted perhaps you could do that, when and if you liked, to cut down expense. On the Dulux website they also give you colours that look good with Self Destruct. (Picture below). Another option is look towards going bold like a strong blue or blue green. Something like in the picture. That's my feature wall, Resene Billabong. ...or a dirty purple or a blood red. It's starting to get really personal of what your tastes are. Perhaps you could Half or Quarter the main house colour in the entranceway so it still flows but gives you more light. Exciting stuff!