I have been trying to find us all some nice official Bersicker art (preferably of the window scene, though I'm not picky) but unfortunately the best I've got are these:
This illustration from the 1975 The Annotated Dracula, drawn by Wilfried Satty
This illustration by Greg Hildebrandt:
Blurry screenshot of Dracula (not Bersicker) smashing Lucy's window (Bram Stoker's Dracula, 1992)
Bersicker (called Berserker in a newspaper article shown earlier) evading capture in the Bram Stoker's Dracula comic by Roy Thomas, Mike Mignola, and John Nyberg:
Bersicker/Berserker from the same comic encountering Mina and Dracula inside the cinematograph:
Bersicker/Berserker escaping the London Zoo in Bram Stoker's Dracula (3:01 to 3:08):
Bersicker/Berserker in the cinematograph in Bram Stoker's Dracula:
This wolf on the cover of Baby's Classics Dracula who may or may not be Bersicker (probably not, as the wolf first appears in Transylvania):
And that's all the official Bersicker I could find. Very sad that there isn't more. Here's an illustration I made of him being yote through a window: