There's a corner of my new mostly-perennial garden that needs filler for a year or two, and I'm thinking annuals, but I don't want to buy hundreds of them and I don't know what to buy! Here's the situation:

This corner also marks our side and rear property lines. We have a lilac hedge on the side, and blue spruces along the back. I think I could work with it if the hedge and the trees met at the corner, but there's a large gap where the previous owners' kids toys had been, right at the corner. We've planted more lilacs to fill in the lines, but it'll take awhile as they're barely knee-high now.

My eventual plan for this corner is to build a 10' round raised planter, with the spruce and lilacs as a living screen behind it. But the planter may not go in for another couple of seasons, and the lilacs will take that long at least to grow up. And the neighbors decided that *now* would be a good time to build a chain-link dog pen in their corner, just behind these dinky lilacs, so I need temporary screening.

I have a three-panel folding metal screen, about 6 feet tall, which I've set up in front of the baby lilacs, and I'm toying with growing some sort of flowering vine on it there to get some vertical interest going. But I'd like more height and "bulk" to that area in general, so that it isn't quite as obviously an area in transition -- even with the screen and vines added, there's this 10-12' empty spot in the corner.

The corner gets direct sun from about 9 a.m. to 3 p.m. in summer, it's sandy and well-drained. What would be good annuals to help me take up this space? I'd prefer something not especially self-sowing because the annuals are a one- or two-season thing at most, but tall and/or wide plants would be dandy. Any ideas?