In addition to the normal units, I'm making an effort to re-create all the Blood Angel specific characters in Charnel Guard form, so far I've done Dante, Astorath, Gabriel Seth, and Tycho the Lost(unpainted).  Sanguinor and Mephiston are next.

Supposedly the text below comes from GW staff, and I have taken things from here and ran with them.  I've expanded on their lore in my head, and have sort of my own idea on how they look/operate.

"As to additional background notes, in addition to those already found in the various FW, FFG and GW books, the Charnel Guard incorporate a mortuary cult into the chapter creed. They preserve the bones of their fallen in extensive crypts as part of their battle barges (which act as their base of operations as they are a fleet based chapter) and have been knwon to decorate their armour and wargear with the bones of fallen heroes and worthy enemies. Macabre reliquaries are a common armorial feature and can be often found incorporated into vehicles and chapter redoubts. The chapter is what Alan used to refer to as of 'chimeric' origin, in that its geneseed is an admixture of several different strains - an attempt by the High Lords of Terra to mitigate the flaws of pure Blood Angels geneseed (the black rage and such). This fact is not widely known and considered secret, nor has it been entirely successful as it replaces several of the known blood angel flaws with the Charnel Guards tendency towards long periods of torpor and an over active sus-an membrane and retaining the enhanced omophagaea common to Blood Angel successors. The other parts of the mix used to create the Charnel Guard is not known, but rumoured to not have been taken from established loyalist legion stocks. Organisationally , the Charnel Guard are more codex based than other Blood Angel successors and maintain a large number of armoured vehicles and dreadnoughts, many of ancient and rare patterns, their dreadnoughts are highly regarded as living ancients and mobile reliquaries by their battle brothers. Their operational preferences are for the use of overwhelming force, assaults with no regard for restraint and permissive of massive collateral damage and civilian casualties. They often make use of psychological warfare and torture in a manner reminiscent of the pre-heresy Night Lords legion, though without the malice that often marked the sons of Nostramo. ” 

An excerpt from Echoes of Eternity:

"Sire!' one of his sons calls, in the flood of retreating warriors.  It is the Bringer of Sorrow, the one who exiled himself to Terra in shame, fighting at the side of the Flesh Tearer.  Two sons that failed him in better times, making him proud now all is almost lost.  He loves them as he loves all his Legion; and though he would never give it voice, his heart always goes out most to the dissappointments, the ones that struggle to reach the perfection the others take for granted."