An interesting query. I will do my best to give you a relevant answer, but can I ask you to clarify the connection between what seems to be an 'Italian' (or at least Mediterranean) ship (Medici; Livorno) and an English ship's cabin? If you are referring to an old model somewhere, it would be good to know about it.
To answer your query I can tell you that there are, as far as is known, no woodcuts, engravings or paintings of the interior of a cabin from this date (the earliest I know of are more than 70 years later) nor have I seen any such features in the background of contemporary portraits. They are still very rare even in much later portraits (I would be very happy to be proven wrong!)
However, there is a simple rule which enables a reasonable start to making a reconstruction of an English cabin at least, which probably applies to other nations at this era. That is, that the interior of the cabins used by senior officers was constructed and furnished to resemble as closely as possible the rooms of the homes in which they lived on land; so look at architecture surviving from that period. Fundamentally, the side walls would be covered with wood panelling up to the dado level, with pilasters at intervals, surmounted by a moulded cornice. The panels above the dado were normally? frequently? sometimes? made not of timber but of fabric. Bulkheads would be all timber construction, probably. The level of finishing of the decoration would depend upon the likely status of the person using it. For someone royal this would involve carving, gilding, elaborate moulded ceilings, and painted ceiling and wall panels too (or maybe tapestries, although this is not mentioned anywhere) Those of lesser status would have cabins without the wall and ceiling paintings, but still with plenty of mouldings, carving and gilding. There are some mentions of the ceiling being painted to match the sky with 'clowdes'.
The completed cabin was furnished with benches, settles and tables; and beds or bedsteads (probably of rope strung over a wooden frame)
This should be enough to enable you to make a good start; and the real guidance is that within the outline of what I have written above, nobody could be more specific for any individual ship of the time, so create what you feel best will fit.
Contemporary evidence for masthead details are pretty much non-existent, and most people will probably rely upon extapolating back from the last known true details from later in the century.
Cornelisz Vroom painted English ships arriving at Flushing in the early 17th century, and some masthead details can be seen in this; I include a small excerpt below. However, although he supposedly depicts English vessels, he probably shows contemporary Dutch practice. The main point to note, though, is that the mast head is shown round. Whilst this is not definitive proof of English practice, it does seem logical that ships whose mast was made of a single tree would not have a square mast-head.
Since at lease Elizabethan times trees for masts had been imported into England from Eastern Europe, so there was no problem finding large enough trees.
An interesting question; I see no problem with accepting that your second picture corroborates the first.
Re the loop of rope used to attach to the yardarm, if one accepts that two anchorage points is better than one, because the load on each leg is much reduced if there are two, then one must conisder how this would work as the yard rises, and the angle of the two legs relative to the yard changes. When the yard is fully lowered, the legs will be at their closest point to being equal, although the inboard one will always be shorter. As the yard is raised, the angle of the lift becomes much closer to the horizontal, and the difference between the leg lengths changes significantly. If the main lift block was simply seized to a bight in the rope at the yard-arm, then, as the yard rises, the inner leg would slacken, and all the stress would be on the outer leg only. By allowing the bight of the rope to move through the sheave of the lower end of a sister block, the stress remains equally distributed through both legs, regardless of how much their lengths change relative to each other.
Mark P's post in Examples of 17th century English galleon commander and officers cabin interiors was marked as the answer