A good pattern has fairly uniform aged larvae or pupae with very few "holes" where the process didn't work -- either the bees failed to prep the cell properly, removed an egg, or removed the larvae or they died and the bees removed them. The queen starts laying about the center of the frame lengthwise and an inch or two below center vertically and lays in a spiral pattern, more or less, so the growing bees in the center are the oldest and emerge first.
The pattern can be spotty in the spring when they first start brooding up because they always collect pollen in large amounts, and only remove the pollen by eating it. That means there will be a number of cells that have too much pollen to clean out for the queen to lay in and she skips them. In year with very heavy pollen collection, the frames can look pretty bad for a few weeks, until they eat the pollen and get back to normal.
Brood frames with small patches of brood, or lots of holes where larvae are "missing", or random aged brood scattered all over indicate problems that need to be addressed.
Both of my hives this year show very nice brood patterns, in fact the deep (between two mediums) does not have significant amounts of honey or pollen in many of the frames, just wall to wall brood as they have brood above and below it as well. I expect them to move honey down later when brood production slows up for the summer and back-fill those medium frames with honey.
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