I think it looks OK but you will probably topple over the bricks as you move around, in particular at the high end as you are reaching over to any plants near the corner of the 2 fences. Chance are it will topple over into any plants that are growing inside the bed there since you are moving in that direction.

That would be my only concern. Otherwise, about 3 tall isn't overbearing enough to fall on its own.

One way to get around it is to build the ground (and additional bricks to support it) in a kind of terrace design. For example, as you have now heard about Bartholomew, his recommendation is for beds that are about 4x4. This is so that you can reach many plants from the outside of the bed.

If you split yours into roughly 4 feet (some go 3 or 5, depending on how they want to break up their bed size), then for the higher end, you will have a higher level of soil to use.

Then with about a 1-2 feet path where you can access the bed on the right or the left, then start your next bed for another 3-5 feet width, but that one will have a lower level of brick wall and thus, soil depth.

Judging by the number of bricks laid out, You could probably get about 2-3 beds plus a path or two in between out of that area, depending on the sizes you wanted.

i think that's good advice -

another thing is that they aren't all that deep - will you did the soil underneath so plants can go below the beds? if it's soil, you would probably want to work in some organic matter/vermiculite etc to allow for drainage. i don't think plants like big gravel between their toes....most anyway,...;)

you say it's 8 - 12" at the shallow end so your bricks are actually quite thick or maybe there are some below your grass level?

i don't think the soil pushing from the inside will topple the bricks - but how much sand/gravel did you put down when you leveled? if you followed the typical guidelines (3-6 inches of gravel, 3-6 inches of sand etc) you should probably be okay - the ground will settle, especially if you dug it up during the project, but if you packed it and put down your base fairly properly, i think you might be okay.

As long as you are in a zone where the ground does not heave from frost/winter, the bricks should stay in place unless you kick them, sit on them etc.

One other consideration. Some people believe that soil heats up faster in raised beds built with brick as opposed to wood. This is probably true and can be a problem for some plants. However, your bed looks relatively shallow, so this might not be a problem.