Cool idea. There are already many dwarven achievements that can be the subject of engravings: making artifacts, death, killing enemies, fighting battles, etc. Coffin and tomb engravings should always be chosen from that list if possible, and then should represent the dwarf's skills starting with the highest:
"This is an engraving of a hammer over a shield. During her life, Unib Melzureth was a Master Armorsmith and produced 215 pieces of armor."
"... an engraving of a sword. Bomrek Keskamlister was an Expert Swordsdwarf and slew a total of 12 enemies."
"... an engraving of a mug of beer. Udib Nomerith became a Legendary Brewer in 1062, and brewed 357 barrels of beverages during his career."[1]
"... an engraving of a ruler and compass. Udib Nomerith was a Dabbling Building Designer, having designed one building."
And positions held:
"... an engraving of a stack of coins. Udib Nomerith served as Bookkeeper from 1055 to 1058."
And maybe other things associated with that dwarf:
"... an engraving of Unib Melzureth holding her son, Udib Nomerith."
"... an engraving of Bomrek Keskamlister's faithful war dog, 'Steeljaw'."
You get the idea. A simple coffin in a one-space tomb can hold only two engravings (the coffin itself and the floor under it), which will usually be date/manner of death and highest skill achieved. A bigger tomb can record more achievements, which is one reason it's such a status symbol.
[1] Ascent to Legendary status is recorded with a date, and takes priority over everything except artifacts. Other skills are just recorded with highest level achieved and total production, and come after death scenes, battles fought, etc.