fully mine: 
-- MainHUDComponents.json (for osu!lazer)
-- mania (except lightings and hitbursts)
-- slider tick

gfx credits:
+----------------------------+------------------------------------------------------------+
| What                       | Where from                                                 |
+----------------------------+------------------------------------------------------------+
| arrow-pause.png            | https://neolurk.org/wiki/Файл:1238521509967.png            |
| arrow-warning.png          | https://osu.ppy.sh/s/414779                                |
| button-*.png               | https://osuskinner.com/element/63/1                        |
| cursor.png                 | rustbell's latest skin                                     |
| fail-background.jpg        | https://gelbooru.com/index.php?page=post&s=view&id=3130827 |
| fruit-*-overlay.png        | https://neolurk.org/wiki/Файл:1238521509967.png            |
| fruit-bananas-overlay.png  | https://neolurk.org/wiki/Файл:Trollface.png                |
| inputoverlay-*.png         | https://osu.ppy.sh/community/forums/topics/564208          |
| lighting?-*.png            | Lunatic Rave 2 (default skin)                              |
| mania-hit*.png             | https://osu.ppy.sh/community/forums/topics/512453          |
| menu-back-*.png            | https://www.reddit.com/r/OsuSkins/comments/4pbvio          |
| menu-background.jpg        | https://web.archive.org/web/20130327020912/http://0chan.hk |
| menu-button-background.png | https://www.reddit.com/r/OsuSkins/comments/4pbvio          |
| pause-back.png             | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| pause-continue.png         | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| pause-overlay.jpg          | https://gelbooru.com/index.php?page=post&s=view&id=3130806 |
| pause-replay.png           | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| pause-retry.png            | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| play-skip-*.png            | https://www.reddit.com/r/OsuSkins/comments/4pbvio          |
| play-warningarrow.png      | https://osu.ppy.sh/s/414779                                |
| playfield.png              | https://web.archive.org/web/20130327020912/http://0chan.hk |
| ranking-*-small.png        | hvick225's skin that used until 2015-2016                  |
| ranking-*.png              | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| ranking-accuracy.png       | osu! default skin (pre-b20130319)                          |
| ranking-graph.png          | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| ranking-maxcombo.png       | osu! default skin (pre-b20130319)                          |
| ready.png                  | https://www.reddit.com/r/OsuSkins/comments/ehbho0          |
| score-*.png                | https://osu.ppy.sh/s/68861                                 |
| scorebar-*.png             | https://osu.ppy.sh/s/414779                                | - modded
| section-fail.png           | somewhere from stock image gallery                         |
| section-pass.png           | https://osuskinner.com/element/33778/8089                  |
| selection-mode.png         | https://osuskinner.com/element/2749/357                    |
| selection-*.png            | https://osuskinner.com/element/11014/2270                  |
| spinner-circle.png         | Burakku Shipu by -Ryosuke                                  |
| spinner-middle2.png        | Burakku Shipu by -Ryosuke                                  |
| welcome_text.png           | https://neolurk.org/wiki/Файл:1238521509967.png            |
+----------------------------+------------------------------------------------------------+
| osu!std skin               | rustbell's latest skin                                     |
+----------------------------+------------------------------------------------------------+

sfx credits:
+-------------------+-----------------------------------------------------------+
| What              | Where from                                                |
+-------------------+-----------------------------------------------------------+
| applause.mp3      | "Love's Joy" by Kreisler (sourced from release ESCL-4390) |
| combobreak.wav    | Counter-Strike (chicken death)                            |
| failsound.wav     | Serious Sam (player death)                                |
| readys.wav        | osu! default skin (pre-b20130319)                         |
| section-fail.wav  | MLG airhorn                                               |
| section-pass.wav  | "Whatcha Say" by Jason Derulo                             |
| spinnerbonus.wav  | Counter-Strike (M4A1 fire, silenced)                      |
| welcome.mp3       | https://www.youtube.com/watch?v=OexrkOwEgTA               |
+-------------------+-----------------------------------------------------------+
| hitsounds         | rustbell's latest skin                                    |
| menu SFX          | Counter-Strike 1.5                                        |
+-------------------+-----------------------------------------------------------+