(I accidentally posted it in /wap/)
I have made a collection of 2ch GIF resources:

AA

Matsucon:

https://web.archive.org/web/20220530052745/http://matsucon.net/material/mona/

https://web.archive.org/web/20220530052745/http://matsucon.net/material/mona/icon01.html

Matsucon (Large and Small size):

https://web.archive.org/web/20220530052745/http://matsucon.net/material/mona/icon02.html

https://web.archive.org/web/20220530052745/http://matsucon.net/material/mona/icon03.html

Matsucon (Animated):

https://web.archive.org/web/20220530052823/http://matsucon.net/material/mona/icon04.html

5channel, NTT Docomo:

https://archive.org/details/2chaagifs

Travelmin:

http://www.travelmin.com/

Nuko:

http://dc.awalker.jp/78/027813/

Other:

https://prcm.jp/list/AA%20%E3%83%87%E3%82%B3%E3%83%A1

Yuru AA:

https://sp.decoraccho.jp/racchoroid/tokushu/tokushu222.htm?intg=tokusyu0201

https://sp.decoraccho.jp/racchoroid/tokushu/tokushu150.htm

Kaomojis:

Kaomoji Kuma:

https://kaomojikuma.com/animated-kaomoji-gifs-japanese-emoticons/

Matsucon:

https://web.archive.org/web/20220530052819/http://matsucon.net/material/mona/icon09.html