Here is the full list of all 99 Pixelarium achievements.
Bigger than 1k pixels
Bigger than 2k pixels
Bigger than 3k pixels
Bigger than 4k pixels
Bigger than 5k pixels
Bigger than 6k pixels
Bigger than 7k pixels
Bigger than 8k pixels
Bigger than 9k pixels
Bigger than 10k pixels
Bigger than 12k pixels
Bigger than 15k pixels
Bigger than 20k pixels
Bigger than 30k pixels
Bigger than 45k pixels
Bigger than 65k pixels
Bigger than 80k pixels
Bigger than 110k pixels
Bigger than 140k pixels
Bigger than 170k pixels
Bigger than 210k pixels
Bigger than 260k pixels
More than 5 colors
More than 10 colors
More than 20 colors
More than 30 colors
More than 45 colors
More than 65 colors
More than 80 colors
More than 110 colors
More than 145 colors
More than 185 colors
More than 210 colors
1k pixels painted
2k pixels painted
5k pixels painted
10k pixels painted
20k pixels painted
40k pixels painted
70k pixels painted
100k pixels painted
150k pixels painted
200k pixels painted
300k pixels painted
500k pixels painted
1M pixels painted
2M pixels painted
4M pixels painted
7M pixels painted
10M pixels painted
15M pixels painted
20M pixels painted
40M pixels painted
70M pixels painted
1 L Finished
10 L Finished
25 L Finished
50 L Finished
100 L Finished
200 L Finished
1 M Finished
10 M Finished
25 M Finished
50 M Finished
100 M Finished
200 M Finished
350 M Finished
600 M Finished
1 S Finished
10 S Finished
25 S Finished
50 S Finished
100 S Finished
200 S Finished
350 S Finished
550 S Finished
800 S Finished
1 XL Finished
4 XL Finished
9 XL Finished
16 XL Finished
25 XL Finished
1 XS Finished
10 XS Finished
25 XS Finished
50 XS Finished
100 XS Finished
200 XS Finished
500 XS Finished
1000 XS Finished
1 XXS Finished
10 XXS Finished
25 XXS Finished
50 XXS Finished
100 XXS Finished
200 XXS Finished
350 XXS Finished
550 XXS Finished
850 XXS Finished