GFX Tools
Here is an extensive list of tools that you can use if you wish to create your own C64 GFX. Kindly compiled by Shine (Andy Zeidler).
Pixel
Multipaint
by Dr. TerrorZ (Tero Heikkinen)
https://drterrorz.itch.io/multipaint
http://multipaint.kameli.net
Pixcen
by CRT (John Hammarberg)
https://csdb.dk/release/?id=215974 (v0.7.0.50)
https://github.com/Hammarberg/pixcen
ALBERT
by TCE (Luigi Di Fraia)
https://www.albertpixels.com
Megapaint
by MonstersGoBoom, Robert Ramsay and Sakrac
https://megastyle.itch.io/megapaint
Project One
by Oswald (Tallósy Zoltán)
https://csdb.dk/release/?id=86776 (v0.6)
Timanthes
by Mirage (Lars Verhoeff)
https://csdb.dk/release/?id=75871 (3.0 Beta)
Ditheridoo
by fieserWolf
https://github.com/fieserWolF/ditheridoo
mcDRAW
by zooperdan
https://mcdraw.xyz
Browser
FunkPaint
by Soci
https://csdb.dk/release/?id=231582 (0.46c)
C64
Amica Paint
https://csdb.dk/search/?seinsel=releases&search=amica%20paint&all=1
C64
Paint Magic
https://csdb.dk/search/?seinsel=releases&search=paint+magic&Go.x=0&Go.y=0
C64
PETSCII
PETSCII (PETSCII Editor)
by Marq (Markku Reunanen)
http://www.kameli.net/marq/?page_id=2717
Petmate
by nurpax (Janne Hellsten)
https://nurpax.github.io/petmate
Petmate 9
by wbochar (Wolfgang-Aaron Bochar)
https://wbochar.com/petmate9
https://github.com/wbochar/petmate9
Playscii
by JP LeBreton
http://vectorpoem.com/playscii
PetPet
by fieserWolf
https://github.com/fieserWolF/petpet
Petscii Cola
by TheTom
https://csdb.dk/release/?id=185842 (v0.5)
C64 ASCII Art Editor
by Egon
https://csdb.dk/release/?id=121059
PETSCII Editor
by krissz
http://petscii.krissz.hu/
Browser
lvllvl alpha
by James
https://lvllvl.com
Browser
Petscii Editor
by fieserWolf
https://csdb.dk/release/?id=155723 (v4.61)
C64
Charcoal
by Lft (Linus Åkesson)
https://csdb.dk/release/?id=162823 (v1.0)
C64
Digital Paint
by The Silver Surfer
https://csdb.dk/release/?id=109143 (v4.0)
C64
Kaleidoscope
by BroBryce64 (Bryce L Tomlinson)
https://csdb.dk/release/?id=130268 (v4.0)
C64
Tyronpaint
by tlr
https://csdb.dk/release/?id=32950 (v2.1)
C64
Board Painter
by Mick
https://csdb.dk/release/?id=24792 (v1.0)
C64
VDC Screen Editor 2
by xahmol (Xander Mol)
https://github.com/xahmol/VDCScreenEditor2
C128
DART (Directory Art Importer)
by Sparta
https://github.com/spartaomg/dart_cpp
https://csdb.dk/release/?id=248771 (v1.4)