The auction, which raised £30,000, is part of a bid to raise £500,000 to build a new adult education centre and modernise Spectrum's existing facilities at its St Erme site in Truro.
The auction was originally intended to take place at a local art sale, but the project snowballed after donations from high-profile artists. Among the lots to have gone under the hammer were drawings from architect Sir Norman Foster, a commissioned portrait of the Queen by Steve Levine and Damien Hirst memorabilia.
In total, Spectrum received more than 100 pieces donated for auction. The items that were not sold on Saturday will be auctioned online, which closes on 30 November. Sarah Miller, the project's main organiser, said the charity was indebted to the artists' generosity.