I learned how to create stickers in telegram because a very talented friend of mine did a great job drawing my "internal multiple personalities" and when we discovered that telegram lets you upload your own stickers I helped her to digitize those drawings and convert them into stickers. So I decided to share with you how you can create awesome customized stickers. And If you're very talented also make extra money by selling your pack to Telegram.

First of all you are going to need:

Computer with Illustrator
Sheet of paperPencil,
pen or markerCamera/scanner
Telegram web version
Creative Market Speech Bubble pack

Step 1: Sketching Our Sticker

Create a drawing of your invention, it could be yourself, some of your friends or any object.

When drawing, try to close all the strokes, and remark the outline since this is going to work as a basis to use later in illustrator.

Keep your drawing the neatest you can. I created a not very elaborate drawing to make it easier.

Step 2: Scan/take a Picture of Your Sketch

Then, we need to scan or take a photo with a HQ camera to create a digital version of our sketch.

What I'm going to do is to create a new file in illustrator and then place our sketch in a new layer.

I'm using a 512 px canvas because that is the size required by telegram for the stickers

Step 3: Use Image Trace to Create Smooth Lines Easily

After placing my picture to the left (because I'm going to add a bubble message in the right side later), I'm going to use:

Image Trace to create smooth lines in an easy way.
Then in the Image Trace Panel, select "Sketched Art", this is very helpful to create smooth lines easily.
I'm still making some adjustments, but of course you can play with all the values to fit your needs.
In my case I only changed threshold to a 118 value.

Step 4: Clean Your Image

As you can see, with Image Trace, some of the shadows were also converted into shapes, so we are going to:

Remove them by using Edit > Image Trace > Expand
Then, right-click over the drawing and "Ungroup"
Delete all the extra shapes we don't want.

Step 5: Color the Paths

Now that we have separated paths, we need to color them by filling the shapes. So, we need to:

Select a path and change the color of the shape.
Repeat the same step with all the parts of your drawing.
You're done! You've colored your drawing :)

Step 6: Placing the Bubble Message

I decided to put a message saying "I love you" for our telegram stickers Pack. I used the resource from Creative Market Speech Bubble pack for the bubble message.

Open the Speech Bubble pack from Creative Market
CTRL + C the bubble you like the most and then CRTL + V in a new layer in the sticker canvas.
Write your message

Step 7: Saving Your Image As Png

It's important to save our picture as png, since we don't want any background.

Go to File > Save for web..
Save it as .png

Step 8: Create a New Stickers Pack in Telegram

We are about to finish, we only need to:

Go to telegram and search @stickers and start a new conversation with the "stickers bot".
Follow the directions to create a /newstickers pack.
Name your pack.
Send an emoji for your first sticker.
Send your .png image.
/publish or add more stickers (Remember you can update your pack whenever you want.
Actually if you consider your stickers are a great art work you can sell them to telegram for 100 USD.