I think you've made a nice start on your landscape. My advice is not to look at it as a project that must be done before moving on to the next one. Plants and soil take way too much time to change. Fertilize and water routinely and it will start to become even better. Take a 5 year view of the work rather than all this fall. I've found it is much less expensive to let mother nature work with you. I'd recommend 2 projects, then move on to painting or whatever and then come back next year for more. Your side area I would simply lay a thick bed of mulch and let it sit for a year. The change in the soil underneath will be surprising and you can come back later with some flowers and shrubs that love shade. A step further would be to add compost under the mulch and some stepping stones in the middle. I'd do pretty much the same with the back slope area except add some ground cover that works well in your area.

The barren side, next to the garage, I think, might best be improved a by: 1) covering the area with some stone and a pathway (be creative with size and texture), and 2) making a raised bed that would leave a 3 foot opening next to the pavement and the edge of the building ( for access) and angle to the property line.

I'll paint most anything, but am not adventurous enough to paint floor tile ;) My M-I-L painted her wall tile years ago, because they stopped using the tub/shower in that room, and it held up amazingly well. Am sure way back them it was oil-based paint. Anyway, if you search this board I'm pretty sure I have seen mention of a product that HD sells that will cling to tile.

You can paint them, but keep in mind that they will not be nearly as durable as the unpainted tile. I would not recommend painting entire tile floors, but accent tiles here and there you may be able to get away with. Follow the normal prep process for painting anything slick....clean, sand, dust, prime with bonding acrylic primer and finish with two coats high quality acrylic paint in satin or higher sheen depending on how shiny the current tiles are.