Heya!
Thank you for reaching out. Unfortunately Humble Bundle doesn't grant you access to the asset packs on my Itch (I wish it did). But I can generate download keys for you here for the packs that were included in your Humble Bundle purchase so you can get access to updates. Please e-mail a proof of purchase for the Humble Bundle that included my asset packs to guttykreum@gmail.com and I'll get back to you as soon as possible.
Thank you again!