I've been trying to put together an armour harness based off Italian armour from the 1430s to 1440s, and I've been able to find good examples of what armour from that time looked like in artwork and artifacts, except for spaulders. I can't find pictures of any spaulders from that time and in artwork you can't really tell what they look like.

Anyone know of any artifacts or artwork that show what Italian Spaulders from that time would've looked like?

I had thought that spaulders (defined as shoulder defenses that did not overlap the breastplate at the armpits) were more popular in the 14th century, and went out of use as full-sized pauldrons came in during the 15th. I suppose some jousting armors had special spaulders that didn't cover the armpit in front or back, but for battle armor I've never heard of spaulders in 15th century Italy, perhaps because of my ignorance. Perhaps that would explain why you can't find any effigies or paintings that depict such a thing.

For pauldrons in art, try Funerary Monument to John Hawkwood and the Battle of San Romano series by Paolo Uccello, Niccolo da Tolentino and Pipo Spano by Andrea del Castagno, UBK 2° Ms. poet. et roman. 3 Giovanni Boccaccio on Manuscript Miniatures, and any more you can think of.

The Italians certainly made many for export, but domestically, they would have been used by infantry, if at all, after the first quarter of the 15th century, I think. There are some large books on Italian frescoes that might reveal something; see if you can get a look at them through ILL.