In some ways, this scene is a genre scene. It takes place in what looks to be a domestic setting and the central character is one that the viewer would be expected to identify with.
Bosch often worked with almost incomprehensible or bizarre iconography. It seems, like the submerged symbolism of Robert Campin's Merode Altarpiece c. 1425 he is inventing or using a now lost lexicon of iconography.
The interior of this composition is formed to look almost as if the scene is taking place within the nave of a vaulted cathedral. This is probably done almost as a sarcastic reference to the Gothic style Church. To the left of the doorway in which a skeleton is entering is a Romanesque or Gothic capital and column.
This image seems to be a sarcastic play on the iconography associated with annunciation scenes such as those by Robert Campin's Merode Altarpiece c. 1425. Almost as in Charles Dickens's A Christmas Carol, in this scene, a miser is being visited on his death bed by a variety of fantastic creatures. Death stands ready in the door to fling his last arrow and take the man to his fate while his soul is wrestled over. God is represented by the apparition of the crucifixion in the window. The light that shines through the window is represented similarly to the soul of Jesus being delivered to Mary in the Merode Altarpiece c. 1425. Above the bed, on a canopy, a demon shines a fake sparking lamp to misguide him.
At the misers back is an angel. Again the angel is similar to representations of Gabriel in annunciation scenes but the miser pays no attention and seems torn, even on his deathbed, between the glory of god and the vain gloria of his avarice represented by the evil frog like demon tempting him with the money bag.
Overall the composition is a vertical one and this plays into the iconography. God is represented at the top of the image and as we descend through the image we can also see that the iconography descends into the common world of man.
Beneath the deathbed is a rather red nosed and almost drunken looking man who has a key and a rosary hanging from his robes. According to the the National Gallery's website, "At the foot of the bed a younger man, possibly the miser at an earlier age, hypocritically throws coins into a chest with one hand as he fingers a rosary with the other."
I think they may have it wrong though, to me it looks like he is placing money into an alm's bowl held by a demon while another demon passes up what looks to be a letter or a papal indulgence. Could this be St. Peter and the chest represent the holdings of the Catholic Church? Perhaps then, the letter is an indulgence that is an attempt to pay his way into heaven.
Beneath the chest and at the very bottom of the picture plane lies a suit of discarded armor. Perhaps a representation of the miser's discarded faith. Notice that the sword is rusted. He is no longer the good Christian soldier depicted in Durer's print.
Here's another point of view but I'm not sure if it's correct:
Bosch's depiction of a dying miser lying in his high narrow bedchamber features a number of details pointing out the consequences of a life devoted to avarice. The figure of death stands in the doorway indicating that the miser's end is rapidly approaching. And while the miser's guardian angel vainly tries to draw his attention to the crucifix in the window at the upper left, the demonic influence is overpowering.
Many commentators have noted that Bosch's work here seems to be of a type which may have been influenced by the Fifteen Century devotional work Ars Moriendi (Craft of Dying) which describes how a dying man is exposed to a series of temptations by demons surrounding his deathbed. At each temptation an angel comforts him and strengthens him and in the end the angel is successful, the soul is carried to heaven and the devil's howl in despair. Here, however, the outcome is much less certain.
The fact that the miser's path was established long before his death is apparent with the inclusion of an image of his younger self placing a coin into a bag held by a demon. Underneath the chest other demons await. in the forefront a winged demon handles the red robes which indicate the miser's earthly rank. While at bedside another creature offers a bag of gold which provides a final distraction to the dying man. The message appears to be that despite God's willingness to provide salvation most people will persist in their sins until the point of death.
Here's the National Gallery of Art, Washington point of view:
Of all fifteenth-century artists, Hieronymus Bosch is the most mysterious. His puzzling, sometimes bizarre imagery has prompted a number of false assertions that he was, for example, the member of a heretical sect, a sexual libertine, or a forerunner of the surrealists. What can be said is that he was a moralist, profoundly pessimistic about man's inevitable descent into sin and damnation.
In this slender panel, probably a wing from a larger altarpiece, a dying man seems torn between salvation and his own avarice. At the foot of the bed a younger man, possibly the miser at an earlier age, hypocritically throws coins into a chest with one hand as he fingers a rosary with the other. In his last hour, with death literally at the door, the miser still hesitates; will he reach for the demon's bag of gold or will he follow the angel's gesture and direct his final thoughts to the crucifix in the window?
Avarice was one of the seven deadly sins and among the final temptations described in the Ars moriendi (Art of Dying), a religious treatise probably written about 1400 and later popularized in printed books. Bosch's painting is similar to illustrations in these books, but his introduction of ambiguity and suspense is unique.
This panel is thinly painted. In several areas it is possible to see in the underdrawing where Bosch changed his mind about the composition. His thin paint and unblended brushstrokes differ markedly from the enamellike polish of other works in this gallery.