This is going into Da Vinci Code territory. The problem is that years ago I explained to a TV producer how one could easily argue a conspiracy of that sort, and made up an example using some beheaded Roman skeletons excavated at York, threw in some random facts and showed how it could become a conspiracy where Caracalla was practicing human sacrifice. The next year the BBC aired the documentary. So ... point made?
Here's the deal. The person who first suggested Amphipolis is shown in the background of Sodoma's painting of the Wedding of Alexander and Roxanne is very brilliant, and so a credible source. The idea is not as nutty as it sounds ... but the evidence is also a case of 2 + 2 + 2 etc all adding up to supposition, but then again that is often the case with archaeological evidence.
According to this theory, the background of the painting would show a view of Amphipolis with the Roman bridge over the river and a large mound whose Lion is hidden by the tree.
However, I need not have cited ancient rhetoricians, historians, and chroniclers like these; in quite recent times the painter Aetion is said to have brought his picture, Nuptials of Roxana and Alexander, to exhibit at Olympia; and Proxenides, High Steward of the Games on the occasion, was so delighted with his genius that he gave him his daughter.The description is pretty detailed, which is unusual for ancient paintings, and we know that it was probably on board rather than a wall since it was portable. Lucian was writing in the 2nd century AD, so the painting predates him, but key question is whether Aetion was a recent painter or one from Alexander's lifetime. The text suggests he was probably working during the Roman period, but that is not a problem if he was depicting Amphipolis.
It must have been a very wonderful picture, I think I hear some one say, to make the High Steward give his daughter to a stranger. Well, I have seen it — it is now in Italy —, so I can tell you. A fair chamber, with the bridal bed in it; Roxana seated — and a great beauty she is — with downcast eyes, troubled by the presence of Alexander, who is standing. Several smiling Loves; one stands behind Roxana, pulling away the veil on her head to show her to Alexander; another obsequiously draws off her sandal, suggesting bed-time; a third has hold of Alexander’s mantle, and is dragging him with all his might towards Roxana. The King is offering her a garland, and by him as supporter and groom’s-man is Hephaestion, holding a lighted torch and leaning on a very lovely boy; this is Hymenaeus, I conjecture, for there are no letters to show. On the other side of the picture, more Loves playing among Alexander’s armour; two are carrying his spear, as porters do a heavy beam; two more grasp the handles of the shield, tugging it along with another reclining on it, playing king, I suppose; and then another has got into the breast-plate, which lies hollow part upwards; he is in ambush, and will give the royal equipage a good fright when it comes within reach.
All this is not idle fancy, on which the painter has been lavishing needless pains; he is hinting that Alexander has also another love, in War; though he loves Roxana, he does not forget his armour. And, by the way, there was some extra nuptial virtue in the picture itself, outside the realm of fancy; for it did Aetion’s wooing for him. He departed with a wedding of his own as a sort of pendant to that of Alexander; his groom’s-man was the King; and the price of his marriage-piece was a marriage.
Sodoma's fresco is on the walls of the Villa Farnesina, which was formerly the Villa (Agostino) Chigi. This Chigi was a great patron of the arts, and employed both Raphael and Sodoma to paint his house, at a time when there was a great re-birth of interest in Classical antiquity (Renaissance).
Although the woman holding a vase on her head may be reminiscent of the Caryatids at Amphipolis, she is in fact based on Raphael, as is the work based on drawings Raphael executed before he died, such as this one:
The Sodoma figure imitates one in Raphael's School of Athens:
This copy of a Raphael drawing is most interesting as it suggests the background might always have been intended:
Here's the problem; Raphael and Sodoma were working long before Pompeii had been uncovered. Whilst the subject of the Wedding of Roxanne and Alexander was popular and often painted on cassone brides took to their new homes ... even the Aldobrandini Wedding was not found until circa 1605, or almost a century later.
One interpretation of this Roman fresco in the 18th century was the Wedding of Roxane but neither this nor other known paintings can be shown to have been the source for Sodoma and Raphael. It is possible that the Roman work of Aetion survived or copies of it did, and that they are now lost.
Records for Rome before 1500 are pretty spotty, although we do have records from the 1600s. For example during the excavation of the site for the Palazzo Barberini in 1626-7 an ancient fresco was found, and soon copied by artists:
This is the landscape which becomes incorporated into the Rubens Feast of Venus in Vienna. The original is now lost.
So the people who've left comments are conflating two 'modern' paintings by Rubens and Sodoma, and two possible ancient paintings and ... honestly, is it possible Amphipolis is in the background of the Sodoma? Yes. Is it likely? No.