Three lines are all Eigner gives us, and they turn on a small surprise. We expect pictures to be silent, something we look at. Here they are "full of / waterfall / echoes," as if the images themselves can be heard. The sense of sight slides into the sense of hearing.
The line breaks do a lot of the work. "Pictures, full of" stops mid-thought, so we hang for a moment before the single word "waterfall" arrives on its own line. Then "echoes" trails after it, like a sound fading. The poem seems to copy what it describes: something big and rushing, then its softer afterlife.
The speaker's feeling isn't stated, but the tone seems quiet and absorbed, maybe a little wistful. Echoes are what is left after a sound has passed, so the poem suggests that pictures, like memories, hold on to something that has already gone. The mood is hushed and spacious, and it leaves a lot of room for the reader to imagine.