i don't have a silver garden but do grow a plant that is quite nice (at times) during the growing season. artemisia schmidtiana 'silvermound" can be tricky to keep looking good but worth the space, in my opinion.
i had some for years in a container and lost it due to neglect last year. i found it again at a box store garden center this spring and planted it in the ground and it is doing pretty well. it has a tendency to die out in the middle and pruning is recommended to deter that. i let mine flower (probably shouldn't) and it got leggy but cut it back and it's looking better. sandy loam soil, sufficient water but not soggy and 6 hrs. of sun is what it gets from me.
it is a plant everyone wants to touch!
i am also trying to get some lychnis coronaria going that i got from my dad. he has the stuff everywhere (north alabama) but i am finding it more difficult to grow.
it has silvery leaves and brilliant magenta flowers.

Here is a link that might be useful: 'silvermound' artemisia

Teucrium fruticans is rated for zones 8-10 but you can certainly give it a chance. I love silver plants but have a hard time with them. I grow the A. schmidtiana but by this time of year it is pitiful. And I love Lamb's Ears but they always rot out. But I keep trying. Linda

just thought of another one i have seen growing in my area but have no personal experience with: leucophyllum frutescens (texas ranger), a desert plant.
they have it growing in a large, brick planter in front of a vet's office and it has been there for years.
according to the link below, it is popular in florida so seems like it can take our humidity if not kept in saturated soil.
i like the looks of the germander you mentioned. where did
you see it for sale? wouldn't mind having one of those. silver foliage and blue flowers are a nice combination.

Here is a link that might be useful: texas ranger

Topsie,
The following grow well for me:
Dicliptera suberecta
Artimisia "Powis Castle" (died after about 6 years)
Stachys "Helene Von Stein" (Lamb's ears; Big Ears)
Stachys byzantina
Lychnis coronaria
All do fine in clayey soil. I have them planted on mounds of soil that I mulch with rocks/gravel.
Artimisia "Silver Mound" rots out in the middle-I had one some years ago.
If you can make it to the swap on Sept 13 at Aldridge gardens, I can bring some of these plants for you.
susan.

Russian Sage (perovskia) has gray-green leaves and light-lavender
flowers that I think goes with "silver" theme. I don't grow it but I've seen
it doing very well in gardens around here. (In full sun.)

Todd

The following do well for me:

Artemisia ludoviciana ssp. albula 'Silver King'
Dusty Miller, Senecio cineraria
Globe Artichoke, Cynara scolymus
Lamb's Ears, Stachys byzanina
Lychnis coronaria (mauve, white)
Mexican Bush Sage, Salvia leucantha
Mountain Mint, Pycnanthemum incanum
Mullein, Verbascum thapsus
Rosemary officinalis 'Tuscan Blue'
Rosemary prostrate, Rosmarinus officinalis 'Prostratus'
Rue, Ruta graveolens
Spanish Lavender, Lavandula stoechas

Thanks everyone. I've already killed most of those plants, but I think I'll try again. Maybe a sandy berm with gravel mulch...Oh, I thought of a pretty plant that has done really well for me...dasylirion berlandieri, weeping sotol. I got it from Yuccado. The terucrium was at Earth Touch in Huntsville. The tag said, "Goes dormant below 20 degrees". Maybe it goes dead...

There is a nice fern I found called "Ghost Fern", don't recall any more of the name. It is a silvery green. I ordered mine from Wayside, but they also have it at Plant Delights Nursery up in NC. I like dealing with them, and their catalog is outstanding.

My soil in the Mobile garden has a good bit of clay below the surface. Of course, I've amended it and it is now covered with a lot of composted leaves and peatmoss and cow manure.