Inspired by my laurel, Isabel Chamberlaine, and medieval painters, I've been collecting shells to prepare paint in (to use like a palette) and with (as a calcium source).
This website has many links to resources about medieval painting and painters including palettes, brushes and grounds:
http://www.larsdatter.com/painting.htm
Real oyster shells found in excavations around London:
http://www.museumoflondonprints.com/image/59557/three-oyster-shells-with-traces-of-pigment-13th-century
Shells as paint holders and palettes in medieval illuminations:
De mulieribus claris (BNF Fr. 598), beginning of the 15th century
http://gallica.bnf.fr/ark:/12148/btv1b84521932/f210.item.zoom
Possible painting from oyster shell: 1420, St. Luke
http://www.themorgan.org/collection/medieval-and-renaissance/manuscript/145545#overlay-context=collection/medieval-and-renaissance/manuscript/145545%3Fid%3D87
St. Luke 1425-30
http://corsair.themorgan.org/cgi-bin/Pwebrecon.cgi?BBID=255341
detail of that page: http://corsair.morganlibrary.org/icaimages/4/m453.014va.jpg
Giovanni Colonna, Mare historiarum, ouest de la France 15th century
http://expositions.bnf.fr/fouquet/grand/f116.htm
Discussion about that page: http://expositions.bnf.fr/fouquet/pedago/dossiers/62/3/index.htm
Hopefully I will be able to read it some day! :)
1450-1460 St. Luke
http://resources42.kb.nl/MIMI/MIMI_76F2/MIMI_76F2_255R_MIN.JPG
1470-80 St. Luke, possible shells?
http://visualiseur.bnf.fr/ConsulterElementNum?O=IFN-8100206&E=JPEG&Deb=44&Fin=44&Param=C
The wise man and the fool in a book of love poetry
http://www.bl.uk/manuscripts/Viewer.aspx?ref=stowe_ms_955_f009~r
Brush tray
http://gallica.bnf.fr/ark:/12148/btv1b84521932/f181.item.zoom
Using pen knife to hold parchment 1480-1490 St. Luke
http://visualiseur.bnf.fr/ConsulterElementNum?O=IFN-8100141&E=JPEG&Deb=32&Fin=32&Param=C
Cutting the pen:
1500 Portrait of a young artist
http://www.artic.edu/aic/collections/artwork/59891
Hand held wooden (?) palettes
De mulieribus claris (BNF Fr. 598), beginning of the 15th century
http://gallica.bnf.fr/ark:/12148/btv1b84521932/f193.item.zoom
http://gallica.bnf.fr/ark:/12148/btv1b84521932/f181.item.zoom
1420 St. Luke
http://corsair.themorgan.org/cgi-bin/Pwebrecon.cgi?BBID=260674
1450-1460 St. Luke
http://resources42.kb.nl/MIMI/MIMI_76F2/MIMI_76F2_255R_MIN.JPG
c. 1460 St. Luke hand held palette and easel
http://www.bl.uk/catalogues/illuminatedmanuscripts/ILLUMIN.ASP?Size=mid&IllID=5740
2nd half 15th c.
http://visualiseur.bnf.fr/ConsulterElementNum?O=IFN-8100206&E=JPEG&Deb=44&Fin=44&Param=C
Mercury's children
http://tarvos.imareal.oeaw.ac.at/server/images/7008627.JPG
1475-1485
https://commons.wikimedia.org/wiki/File:Hausbuch_Wolfegg_16r_Merkur.jpg
1490-1500 Zeuxis
http://www.bl.uk/catalogues/illuminatedmanuscripts/ILLUMIN.ASP?Size=mid&IllID=38631
1495 St.Luke
http://resources42.kb.nl/MIMI/MIMI_135G19/MIMI_135G19_027V.JPG
15-16th century Timarete
http://visualiseur.bnf.fr/ConsulterElementNum?O=IFN-7904118&E=JPEG&Deb=1&Fin=1&Param=C
1500 St. Luke
http://www.bl.uk/manuscripts/Viewer.aspx?ref=add_ms_35313_f012v
1505 Niklaß Kerner
http://www.nuernberger-hausbuecher.de/75-Amb-2-317-123-v
c. 1500-1525 St. Luke in a book of hours (MMW 10 E 3, fol. 19v),
http://resources42.kb.nl/MIMI/MIMI_MMW_10E3/MIMI_MMW_10E3_019V_MIN.JPG
1510 St. Luke
corsair.themorgan.org/cgi-bin/Pwebrecon.cgi?BBID=260606
The Miracle of St. Francis of Paola, 16th century
http://balat.kikirpa.be/photo.php?objnr=40001697
St. Luke by Niklaus Manuel
http://www.wga.hu/art/m/manuel/lukepain.jpg
1520 St. Luke
http://corsair.themorgan.org/cgi-bin/Pwebrecon.cgi?BBID=253264
1524. St. Luke in a book of hours (MMW 10 F 33, fol. 15v) by Jehan de Luc
http://resources42.kb.nl/MIMI/MIMI_MMW_10F33/MIMI_MMW_10F33_015V_MIN.JPG
1532 St. Luke
http://www.wga.hu/frames-e.html?/html/h/heemsker/1/lukepain.html
1530-60 St. Luke
http://www.wga.hu/frames-e.html?/html/h/heemsker/2/luke_pai.html
1548 Self-portrait of Caterina van Hemessen
http://www.wga.hu/frames-e.html?/html/h/hemessen/caterina/selfport.html
c. 1556 Self-portrait of Sofonisba Anguissola
https://en.wikipedia.org/wiki/File:SofonisbaAuto.jpg
1558 Self-portrait of Anthonis Mor
http://balat.kikirpa.be/photo.php?objnr=40002685
after 1565 St. Luke painting the Virgin.
http://www.wga.hu/html_m/v/vasari/2/11annunz.html
c. 1575-1609 A young painter seen from behind by Annibale Caracci
http://www.britishmuseum.org/research/collection_online/collection_object_details/collection_image_gallery.aspx?assetId=63109001&objectId=714719&partId=1
16th century http://www.photo.rmn.fr/archive/12-505617-2C6NU0WKA1MQ.html
1580s by Annibale Caracci
http://posner.library.cmu.edu/Posner/books/pages.cgi?call=390_S89N&layout=vol0/part0/copy0&file=0031
1584 Otto Venius painting, surrounded by his family
https://commons.wikimedia.org/wiki/File:Otto_van_Veen_-_The_Artist_Painting,_Surrounded_by_his_Family_-_WGA24343.jpg
1590 by Jacob Willemsz Delff
http://www.wga.hu/art/d/delff/jacob1/a_family.jpg
16th century self portrait Cornelis Cornelisz van Haarlem
http://balat.kikirpa.be/photo.php?objnr=20022289
16th century
http://www.photo.rmn.fr/archive/10-512024-2C6NU0QZOQYF.html
16th century, a young man seated with his palette
1602 Marten Vos, St Luke painting the virgin
http://www.wga.hu/html_m/v/vos_m/lukepain.html
1603? Portrait of the Artist's Son Jorge Manuel Theotokopoulos by El Greco
http://www.wga.hu/frames-e.html?/html/g/greco_el/15/1511grec.html