I did such script a long time ago.

I should start by asking, how much disk space do you have for this?

Local images are cheap:

+--------+---------+
| number | size    |
+--------+---------+
|     22 | 2108819 |
+--------+---------+

eswiktionary
+--------+--------+
| number | size   |
+--------+--------+
|     14 | 390539 |
+--------+--------+

frwiktionary
+--------+--------+
| number | size   |
+--------+--------+
|      6 | 702706 |
+--------+--------+

dewiktionary
+--------+---------+
| number | size    |
+--------+---------+
|    104 | 4943453 |
+--------+---------+

enwikiquote
+--------+------+
| number | size |
+--------+------+
|      0 | NULL |
+--------+------+

eswikiquote
+--------+------+
| number | size |
+--------+------+
|      0 | NULL |
+--------+------+

frwikiquote
+--------+------+
| number | size |
+--------+------+
|      0 | NULL |
+--------+------+

dewikiquote
+--------+---------+
| number | size    |
+--------+---------+
|     17 | 2236129 |
+--------+---------+

enwikibooks
+--------+-----------+
| number | size      |
+--------+-----------+
|   2716 | 153301990 |
+--------+-----------+

eswikibooks
+--------+------+
| number | size |
+--------+------+
|      0 | NULL |
+--------+------+

frwikibooks
+--------+---------+
| number | size    |
+--------+---------+
|    169 | 8244783 |
+--------+---------+

dewikibooks
+--------+------------+
| number | size       |
+--------+------------+
|   7697 | 2772943547 |
+--------+------------+



but the commons files will start requiring a bit more space (about 1 TB):

enwiktionary
+--------+--------------+
| number | size         |
+--------+--------------+
| 724855 | 154587222013 |
+--------+--------------+

eswiktionary
+--------+-------------+
| number | size        |
+--------+-------------+
|  18938 | 12918158214 |
+--------+-------------+

frwiktionary
+--------+--------------+
| number | size         |
+--------+--------------+
| 560321 | 146933557784 |
+--------+--------------+

dewiktionary
+--------+-------------+
| number | size        |
+--------+-------------+
| 933737 | 84462331479 |
+--------+-------------+

enwikiquote
+--------+-------------+
| number | size        |
+--------+-------------+
|  55186 | 98435989071 |
+--------+-------------+

eswikiquote
+--------+------------+
| number | size       |
+--------+------------+
|   5712 | 7522618990 |
+--------+------------+

frwikiquote
+--------+-------------+
| number | size        |
+--------+-------------+
|   7348 | 11151209748 |
+--------+-------------+

dewikiquote
+--------+------------+
| number | size       |
+--------+------------+
|   4211 | 6149070638 |
+--------+------------+

enwikibooks
+--------+--------------+
| number | size         |
+--------+--------------+
| 106405 | 133670795995 |
+--------+--------------+

eswikibooks
+--------+--------------+
| number | size         |
+--------+--------------+
|  44309 | 122871671629 |
+--------+--------------+

frwikibooks
+--------+--------------+
| number | size         |
+--------+--------------+
|  98843 | 248629243582 |
+--------+--------------+

dewikibooks
+--------+-------------+
| number | size        |
+--------+-------------+
|  69669 | 54020348470 |
+--------+-------------+

All of them:
+---------+--------------+
| number  | size         |
+---------+--------------+
| 2021173 | 981218142389 |
+---------+--------------+





for wiki in  enwiktionary eswiktionary frwiktionary dewiktionary enwikiquote eswikiquote frwikiquote dewikiquote enwikibooks eswikibooks frwikibooks dewikibooks; do echo $wiki; sql "${wiki}_p" "SELECT COUNT(img_name) AS number, SUM(img_size) AS size  FROM image;"; echo; done
for wiki in  enwiktionary eswiktionary frwiktionary dewiktionary enwikiquote eswikiquote frwikiquote dewikiquote enwikibooks eswikibooks frwikibooks dewikibooks; do echo $wiki; sql commonswiki_p "SELECT COUNT(img_name) AS number, SUM(img_size) AS size  FROM image WHERE img_name IN (SELECT DISTINCT gil_to FROM globalimagelinks WHERE gil_wiki='$wiki')"; echo; done
SELECT COUNT(img_name) AS number, SUM(img_size) AS size  FROM image WHERE img_name IN (SELECT DISTINCT gil_to FROM globalimagelinks WHERE gil_wiki IN ('enwiktionary', 'eswiktionary', 'frwiktionary', 'dewiktionary', 'enwikiquote', 'eswikiquote', 'frwikiquote', 'dewikiquote', 'enwikibooks', 'eswikibooks', 'frwikibooks', 'dewikibooks'))  ;