Those two blue bottles? Those are +1/+1 counters waiting to be applied -- mouse over the art to see them highlighted.
Okay, but what about some other ways that +1/+1 counters have been portrayed in the art? Consider the case of the Cytoplast creatures from Dissension. Here's the Cytoplast Manipulator:
Once you mouse over the image, you'll see that each of her hands are enhanced with Cytoplasts. Two Hands = Two +1/+1 counters. By contrast, Cytoplast Root-Kin has cytoplasts on both hands and both feet—and has four +1/+1 counters!
Dragon Blood gives one +1/+1 counter at a time. Let's take a look at how Ron Spencer portrayed that in Mirrodin:
Of course, not all +1/+1 counters are portrayed so literally. Take, for example, the case of Daily Regimen:
That's just a giant doing exercises. But as long as we're here, mouse over the art to see the logical result of all that exercise. That giant should really consider switching arms.