They will take place twice a year, with the first scheduled for December 17 under the title British and Continental pictures.
The move coincides with the decision to highlight the range of traditional expertise coming together under one roof to offer a varied programme of sales by creating a new website, www.25blytheroad.com, to promote their activities.
Silver and works of art specialist Matthew Barton and maritime and scientific specialist Charles Miller, who have both held their sales at Blythe Road for some years, remain at the centre of the business along with Mr Del Mar.
George Duckett, head of operations, is overseeing the new picture sales, which will be held under the 25 Blythe Road banner.
Amy Kitchen, who has been assisting Matthew Barton and has an art history and design background, has created the new website, which incorporates plans for timed online auctions.
The December paintings sale is expected to be the first of these.
"Each specialist company will retain its individual identity and will continue to hold live sales at Blythe Road, but by presenting ourselves as a specialist hub of auctioneers, we believe that we will reap the benefits of our critical mass more effectively," Mr Del Mar told ATG.
"The exponential rise in online bidding in our live sales as well as the approach by other leading auction houses in holding purely online auctions has been a major contributing factor to our decision to hold the first paintings sale here exclusively online.
"We anticipate selling pictures from around £200 to £7000 and there will be a conventional public viewing on the premises at Blythe Road in the days prior to the sale."
Mr Del Mar said the reason for going into pictures was that "there did not appear to be a specialist focus in what many have defined as lower-value paintings, and we believe that there is a need for new collectors, decorators and sellers at this level".
He added: "Our shared experience is that collectors enjoy participating at all levels of the market, and although we sell individual items sometimes for hundreds of thousands of pounds, we feel that it is important to ensure that collectors are looked after at all levels."