Another suggestion for a sponsored discussion.
There are artists who paint pictures and sometimes sell the originals and sometimes choose to keep them.
They also get a high quality photograph of their picture made and then sell a limited edition of fine art prints, sometime framed, sometimes not framed, sometimes with a choice for the purchaser.
They sometimes also get A5 size greetings cards featuring the painting, and then these get packaged in clear envelopes and sold, some directly from the artist, some from visitor centres and some from shops.
Such cards often have the name of the artist, a postal address of his or her studio or gallery, and a website address.
So maybe a sponsored discussion led by such an artist from, say Thursday morning to the next Wednesday evening, with the artist reading and posting from time to time during that week would be good. So something for everybody interested in art, ranging from around £2 for a card to perhaps £500 for an original with a framed print somewhere in between. Perhaps far more effective for an artist than just a static advertisement.
The cards are often of what is known as the blank card type in that the inside of the card is blank, so if used as a greetings card the sender may use it for any occasion as desired.
There is also the following site, I have not bought anything there as yet, but maybe that business might like to hold a sponsored discussion.
www.theblankcardcompany.co.uk/index.html
Sometimes people buy a blank card to send, sometimes to keep, possibly framing it, sometimes buying two the same - one to send, one to keep.
A blank card framed in an oak effect frame can look quite spectacular, and not be very expensive.
www.tesco.com/groceries/en-GB/products/308622478
I have never found a frame designed for A5 size, but that may be because a lot of frames are sold to suit the sizes often used for photographs, so a frame for 10 inches by 8 inches is larger than needed, but the effect is quite distinctive.
Framing a card is good, even if the framed picture is usually stored in a drawer or cupboard due to lack of wall space as it is an art object and less likely to be forgotten or discarded.