I tend to picture my dwarves as... dwarves, obviously. And as per the 'our dwarves are all the same' rule, they're bearded, construction-and-digging-loving... well, dwarves. Also constantly guzzling brew and never getting drunk.
If I raise a militia to defent my fortress, they usually fail to gather any useful equipment except for a few weapons, so they probably look like a ragtag band of dwarven-equivalent-of-peasants clutching picks, axes, boulders and whatever they picked up along the way.
Fisherdwarves summon the image of a peaceful dwarf with a fishing pole or one throwing a net. Metalsmiths tend to be pictured with gray/black beards, for some reason, with wood burners being even more black. Herbalists make me think of a dwarf with a pouch/bag carefully searching a bush for berries. Masons are grey/white with stone dust from all the frantic building they usually do in my forts. Mechanics are agile dwarves with braided beards and wearing work clothes with tools of their trade tucked into many pockets. Pump operators are often stout, overly strong dwarves wearing frayed clothing with no sleeves and working with magma lighting the surroundings (even when they are not pumping magma, I still get that image). Miners are perpetually dusty and always clutching their picks. Various crafters and especially jewellers bring up the image of a dwarf with a magnifying monocle and a carving tool carefully working on whatever their thing of choice is.
Also, the amount of decoration on the dwarves' items on those images depends on their skill level and how 'unmanual' their labour is, and their clothes' colours generally bear something in common with their profession. Nobles wear richly decorated purple, mechanics-related professions wear reddish leather workclothes of various designs, farmers wear simple undecorated clothing, crafters' clothes have something coloured blue etc.
And yes, every dwarf has some sort of an image.
Recently I tried a hammerdwarf adventurer, and discovered that he was armoured in a most unusual way - he wore tons and tons of cloth under the bits of armour he had, including a dress. I pictured him as a walking metal cloth bin armed with a hammer and a shield.