I'm curious to know that what style of art you're ultimately working towards? Like, if knowledge/ability was put aside, which genre of art you'd see yourself mostly doing? (I see you testing a lot of different styles and was kind of curious to know if you tended to favor any particularly - just so I can understand you as an artist better, since I really don't know you all that well yet when everything's said and done.)
The life stuff is looking good. I like the piece that's the guy in the loin cloth (from behind) with the spear and then the studies from the park the best out of the bunch. Also, that piece that's the night scene -- reverse white on black. That's pretty cool, too.
On some of your figures, I'd ease up on the thickness/darkness of your outlines. When your outlines are darker than the shadows on the figure, it makes it feel kind of flat/cartoonish. (Darker edges just seem to make it more difficult for a form visually to turn in 3D space. I think it's the abruptness of the edge - it's so dark, and then there's nothing, so it feels flat. Lighten it up a bit and I think your figures will jump ahead. Your graphite stuff, for instance, has a much better balance of edges/shadows than your charcoal stuff. Granted, the graphite probably has a much finer edge than the charcoal you're working with, but lighten your hand up with the graphite to compensate a bit. Try to draw with more confident lines, too, and get rid of the 'sketchy' feeling. It's easier said than done, I know -- I struggle with it at times, too.)
The comments about dark edges/thick line work applies to your digital stuff, too. You don't need to sketch with such thick lines -- it's making it much harder to see the true nature of some of your shapes. And, if you try to paint over the thick lines, it can throw your proportions off, too. Take, for instance, the sketch of Joe Manganiello. Is the actual figure designated to the painted areas or are the outside edges of the black outlines the actual edges of his figure? That'd be a pretty big difference proportion-wise in some areas if you paint over the outlines, or if you were to simply delete them. One would be considerably bigger in parts than the other. If you sketch with thinner lines, however, you'll get a much more accurate judge of proportions/shapes, especially if you're planning to paint things after the sketch. (I hope that makes sense the way I worded it. XD ) Try to make your digital brush the size about the size of an actual pen tip and see how you do sketching with that -- I bet your sketches will be much easier to read and work with. (Think of how much easier it would be to paint in the life sketch of the guy with the loin cloth and the spear vs. painting in your sketch of Joe, for instance. Especially if you decide to delete the sketch when you're done -- you'll wind up with something much more consistent. If you were to paint in the sketch of Joe around the lines you currently have, you'll wind up with gaps in the paint if you delete the line work, which makes it almost useless to lay the paint down beforehand -- you'd wind up with something that looks more like pieces of a puzzle on your paper than a solid figure.)
Also, digital tip: Always tone your background before you start painting. If you paint your colors (or even just values) against white, you're going to have a hard time judging their true intensity/value accurately. (How can you tell how light or dark something is when it's just against stark white? Everything is going to look darker when compared against it so, if you decide to put a background in there after the fact, it'll throw all the values you've already laid in off because now you'll actually have something to compare them against. It makes it very hard to make your figure feel like it's meshing with the intended environment if you do the process in reverse. You don't have to go crazy -- just lay down a neutral medium-value/color and you're good to go, kind of like you have in the piece with Joe. It'll help you to get the most out of your lighting and your shadows. Notice how much easier it is to establish lighting, for instance, in your Joe piece than in your other piece with just the guy's face? You can tell where the lights and darks are on Joe instantly, but the face is much harder to judge the lightest of lights because they're almost exactly the same as the background. You throw a background on the face piece, it'll change the intensity of the already established values entirely.)
As far as Caravaggio goes, I think it's kind of cool that you're working from an actual print instead of one off the computer. It would make it harder to make sure the canvas size is the same (obviously) but, I think if you can at least keep the proportions/edge dimensions generally the same, you'll be in good shape for eyeballing the placement of things in the painting. (You could always just grab a cap of the painting off google and use the general dimensions of the image for your canvas, then toss the picture itself and use your print as your actual reference. That's probably what I'd do and save myself a bit of headache trying to figure out how big the edges should be by actually measuring them out and then trying to translate that into my computer.)
Glad to see you're getting so much done with summer approaching. (I know that this time of year with school is crazy, trying to wrap everything up!) Keep up the hard work -- Looking forward to your next update! ^_^