@gpabm I partially agreed to you. Actually I did the de-dup work, but then I realized it's hard to determine which one to be left, so I reverted my work. Some of pictures are pretty similar but still not exactly same, which are all reserved. Very few are just in different sizes, which should be cleared, but their number is really little. Most of the duplicates (true duplicates, totally same in even a single byte), are among their own series, which are composed into individual "tweets". If I delete those duplicates, the related series are incomplete and the "tweet" is then intact. So I decide to not touch them. Then I realized that there was few to be de-dup, So I just keep them all.
Any way, it's the author who repeatedly upload his old artworks into new tweets. All I did was just downloading those tweets. I did remove all those non-artwork photos thoght, even some of them are very interesting.