Many accessories can be put on a backpack, depending on the intended use of the backpack and personal preference. Here are some examples:

1. Water bottle holder - This can be a pocket or a loop on the side of the backpack that securely holds a water bottle.

2. Chest strap - This helps to distribute the backpack's weight more evenly and prevents it from bouncing around while walking or hiking.

3. Hip belt - Similar to the chest strap, this helps distribute weight and prevents the backpack from shifting around while walking.

4. Compression straps - These straps are used to compress the backpack and make it more streamlined, which is useful when carrying bulky items.

5. Rain cover - This cover covers the backpack to protect it from rain and keep its contents dry.

6. Pockets - Additional pockets can be added to the backpack to hold items such as keys, a phone, or snacks.

7. Trekking pole holder - This is a loop or attachment that holds trekking poles when they are not in use.

8. Reflective material - Reflective strips or patches can be added to the backpack to increase visibility in low-light conditions.

9. MOLLE webbing - This loop system can be used to attach additional gear to the backpack, such as pouches or water bottle holders.

10. Hydration bladder - This bladder holds water and fits inside the backpack, with a tube allowing easy drinking while moving.

There are many ways you can spice up your backpack! Here are some ideas:

1. Add patches - Find cool patches representing your interests or hobbies and sew them onto your backpack.

2. Use iron-on transfers - Create your designs or use pre-made iron-on transfers to add flair to your backpack.

3. Personalize with paint - Use fabric paint or markers to add designs or quotes to your backpack.

4. Attach keychains - Find some fun and unique keychains and attach them to your backpack to give it some personality.

5. Add buttons - Collect fun buttons or pins and attach them to your backpack.

6. Customize with stickers - Decorate your backpack with your favourite bands, movies, or TV shows.

7. Tie-dye - Use tie-dye to give your backpack a unique and colourful look.

8. Embroidery - If you have some embroidery skills, you can add intricate designs to your backpack.

9. Add fringe or tassels - Use fabric or yarn to add some fringe or tassels to your backpack.

10. Switch up the straps - Find funky or colourful straps to replace the ones with your backpack.

Remember, there are no rules for spicing up your backpack, so have fun and get creative!

The things that you hang on your backpack are called accessories or attachments. However, there are some specific terms for certain accessories that are commonly attached to backpacks, such as:

1. Carabiners - A type of clip used to attach gear to the outside of a backpack.

2. D-rings - A type of metal ring sewn into the backpack, which can be used to attach accessories.

3. Trekking pole holders - A loop or attachment on the backpack that holds trekking poles when not in use.

4. Water bottle holders - A pocket or loop on the side of the backpack that securely holds a water bottle.

5. Gear loops - A series of loops on the outside of the backpack that can be used to attach gear or accessories.

Overall, the term "attachments" is probably the most general term to describe the things that are hung on a backpack, as it encompasses all types of accessories and gear that can be attached to the backpack.