Yet ev'n these bones from insult to protect, Some frail memorial still erected nigh, With uncouth rhymes and shapeless sculpture deck'd, Implores the passing tribute of a sigh.
Even though these poor villagers don't have big fancy monuments or "trophies" over their graves, they at least still have frail, flimsy memorials nearby, if only to protect their remains from the insult of having people picnic or play cricket on their graves.
These flimsy memorials aren't made out of fancy marble—they just have rough, shapeless sculptures to ornament ("deck") them, and are decorated with crude, uncouth poetry.
But even though the memorials aren't all fancy, they still inspire passersby to pause long enough to sigh. So there!