Beginner Gardening: Need new plant ideas- garden looks sparse, 1 by breathehope

breathehope wrote:
I planted a new kidney-shaped garden in my narrow backyard. I couldn't extend it to the alley because of the underground lines.

I spaced out the plants according to design, but the garden looks empty. The bareoot tree (american redbud) I bought is small but grows up to 25 feet high . The butterfly bushes can also grow up to 8 feet high and wide. The Indian Hawthorne is on the left (Rosalinda) and there are eunonymus on the right. There are small plants that I bought at Michigan bulb that are so small you cannot see them. I regret it now, because it will take more than a season for them to even be seen.

Any ideas to how I can make the garden look fuller without breaking the budget and accomodate the space needed for the main plants?