First:

Open your GIMP with your own size. I chose 400 x 600 as usual. LOL

After that, open your picture and set it as layer. File > Open as layer:

Duplicate it more than 2. I duplicated it 6 times, including the main one:

Open a new and different picture that you want.

I used Hoya and put it on top of Dongwoo’s pictures:

Again, duplicate it 6 times:

Click on the last picture of Hoya, the most below:

Go to Filters > Blur > Motion blur. A window will pop out like this:

Do the same like I did.

Do same with Dongwoo’s picture
.

Go to Filters > Animation > Optimize (for GIF).

A new canvas will come out. Go to Filters > Animation > Playback.

And you’re done! I did an edit with the background too. You can edit the background or use your own creativity to decorate it. Ask me anything and I’ll try to help you. Good luck!