If this hasn't been posted yet, Jellyneo has a good, if not all, item list of possible weekly streak rewards (and daily rewards but I didn't look at it lol)
(you need an account to see links)
If you don't want to look it up, here's a list:
10th Birthday Illusen Birthday Book
AAA Collectable Charm
Altador Cup Food Court Background
Altador Cup Tailgate Party Background
Angry Techo Fist
Babaa Hand Puppet and Miamouse Finger Puppet
Bendy Sword of Skardsen
Black Currant Gummy Kiko
Blobikins
Candy Paint Brush
Chocolate Crown of the Faeries
Cyodrake
Diet Big Gulp Neocola
Draik Transmogrification Potion
Esophagor Plushie
Faerie Kadoatie
Faerie Krawk Morphing Potion
Friendly Cultist Plushie
Frost Lizard Plushie
Game Controller Collectable Charm
Gelert Transmogrification Potion
How to Earn NP The Easy Way
Ice Hissi Morphing Potion
Invisible Paint Brush
Jelly Negg
Kadoatie
King Altador Stamp
Krawk
Kreludor Mining Corridor Maps
Lab Ray Stamp
Limited Edition Evil Chia Plushie
Lost Desert Paint Brush
Maraquan Commanders Helm
Pastel Paint Brush
Pink Petpet Paint Brush
Plushie Poogle Morphing Potion
Purplum Tonic
Rainbow Candy Floss
Reject Red Acara Plushie
Sleep Ray
Sloth Collectable Charm
Snowbunny Stamp
Soup Faerie Doll
Space Faerie Doll
Tooth Faerie Doll
Spring Gift Basket
Squishy Krawk Plushie
Star Gazing Background
Stealth Paint Brush
Strawberry Shoyru Hand Puppet
Taiko Standing Drum Collectable Charm
The Mystical Tablet
The Secret Altadorian Spring
Toy Paint Brush
Two Rings Arcmagus Plushie
Valentine Fyora
White Ixi Plushie
Ylana Skyfire Sitting Plushie
Ylanas Summer Adventure Tales