Picking up life size converter and exploring marco photography has been a great "photo exercise."
A "photo exercise" for me is just picking up the camera and exploring different subjects, cameras, or techniques learned along the way. This is something that evolves if you do it on a regular daily basis. That evolution occurs when a high level of understanding comes between your subject, what you've learned prior, and exploration of endless possibilities mesh together. The key here is that exploration part comes with the shear desire to pick up your camera and use it. If you take pictures and have a passion for it, you know what it is like when you find that shot and it excites you to "get that 1 shot." This can come in many forms - from a live passing event to stills by yourself in total darkness.
Exploring macro I've gained a further appreciation of space, details, and that little things can make the biggest difference. A tripod is almost a must for macro work, while not all of these shots are using a tripod, I tend to think you can probably pick the ones that aren't? Using a fill card can be extremely helpful to provide that little extra boost for back lit subjects.