SFGate

lcgrcondo I am concerned that a planter would take up too much space and just get in the way. Instead I would a piece of art on the left wall. The weather-friendly piece of art would add visual interest without taking up space.

msmorales Have you seen those awesome containers of succulent plants? They basically take a shallow (2" deep) square, fill with some kind of light soil substitute and then cover it with an open grid. Then plant completely full of succulents of many varieties, and hang vertically. Stunning! Google "vertical succulent garden" and you'll get some real inspiration!

silvisideas I think a diamond shaped trellis with a jasmine or similar climbing plant. On both side of your porch.

Jayme Hobbs Narrow, long rectangular shaped could sit there/and could have a trellis with a climber/or just a variety of plants, with some taller ones.

Susanna I vote for decorative birdcages. you can find narrow ones and they add character and whimsy. if you look around you can find them online and places like home goods. if you don't like the color you can spray paint them all alike. Nail them to the wall and fill with moss, dirt and small plants. i put violets in mine and pansys. Here is one-pricey-but will give you an idea of what I mean.
http://www.amazon.com/Decorative-Bird-Cage-Mirror-Decor/dp/B0063Y20UK/ref=sr_1_13?s=pet-supplies&ie=UTF8&qid=1358657205&sr=1-13

Susanna Oops, I meant pansies.

mveasey You could attach something on the side, as in photo, or I would simply do one tall one as in the second photo on the lower right. Boxwood always looks classy. I would buy an inviting doormat.
If all fails, you could hang two allyear wreaths on the doors for a little green welcome.

Greenblott Landscape Design You may consider a green wall or simple product such as a Woolly Pocket.

JWinteriors Since you use primarily the one door, i would add a larger rug, a small bench with a wrought iron rectangle above it. A colorful cushion or pillow on the bench. A potted plant beside it.