Since time immemorial, people have wanted to draw. And ever since the first middle-schooler picked up a pen, people have wanted to draw on themselves.

For creatures with soft, dye-agnostic skins such as humans, decoration can be as easy as doodling with graphite or a plant dye, or as in-depth as applying tattoo ink under the skin. Depending on the method of application, marks can last till death and beyond, or may be washed off at the end of the day.

For those with scale and chitin looking for long-term decoration, things can be a bit different. Tattooing equipment can get expenisve fast when it has to be designed to penetrate materials that are purposefully difficult to penetrate. For those who shed, tattoos may also be lost or damaged during sheddings. Markers and dyes are much more common solutions. A humble Sharkey marker will apply well to scale, but will come away with some time. For the very short term, dry-erase markers are an excellent option. And there are specially designed markers that last for a long while, even on chitin.

Those with fur may face a greater challenge, as tattoos done with normal ink do not show up through most fur. Reizopigment, on the other hand, shines through like a beacon. Fur and hair dye are certainly an option, but the marks may lose their shape as the hairs continue to grow. Careful trimming can create some truly lovely effects, especially for those with brindle coats. This can also be incredibly high-maintainance depending on the size of the patch and the amount of detail needed. Scarring is an option for more long-term marks, but it is hard to reverse and generally not considered a good idea.

Currently doing a project on furgonomics and technology in a modern, low fantasy setting and musical instruments are a thing I hadn't considered. Until now. Some ideas off the top of my head:

+ The piano is one of the more universally accessable instruments, but there is some difficulty in the fact that not every species has the same size hands. Or even the same number of fingers.
+ Bowed string instruments are also pretty accessible, but once again, size matters. You probably won't see a Kobold playing the double bass or a human playing the quarter violin.
+ Percussion is fair game as well. I don't know enough about it to go off on a tangent though.
+ Humans have a monopoly on some brass and woodwind instruments since they have The Lips for it. Double reed instruments especially.
+ Vocals, on the other hand, are dominated by avian species since they have The Chords for it. There's been a recent trend of using one's voice to pretend to play an instrument you wouldn't physically be able to. Like that one video of the crow jamming out very convincingly on the trombone and just carrying on when the slide falls out.
+ Someone invented a version of the bagpipes that has an accordion-like pump and can be played by almost any species, provided they are trained in the operation of it. The original design took three people to operate and resulted in the inventor being disbarred from the Guild of Musicians for being "too damn loud". They promptly joined the Guild of Artificers and were warmly welcomed.

Help I tried to come up with logical explanations for Darkvision and they're kinda rubbish
Option 1: Single-frequency Emissive Darkvision. The user emits light, usually from the iris, at a wavelength outside the scope of other species, then uses extra-sensitive cells in the eye to pick up reflections. The wavelength is usually somewhere in the infrared, but ultraviolet sensitivity is occasionally seen.
Emissive Darkvision allows some semblance of black-and-white vision in otherwise total darkness. The ability increases in effectiveness the more nearby creatures using the same wavelengths.

Option 2: Thaumovision. The user emits tiny pulses of magic and uses modified eye cells to detect the reflections. Similar issues and advantages to Emissive Darkvision, with the added benefit that it is sensitive to spells that are not perfectly put together. Which is to say, all spells.
Thaumovision can be very useful for detecting enchantments or illusions, but a badly-woven spell can be as bright and distracting as a welding torch would be in normal vision.

Option 3: Weak Reizosense. Allows a survey of local reality. The user extends an array of metaphorical whiskers to feel the area around them, giving them an idea of where objects are. If a whisker hits something real, the user knows how long it is and how dense the thing it hit is. The whiskers can be aimed to all point at a specific spot, giving the user a fair view of the object.
Weak Reizosense is very good at detecting moving things in a short area around the user, especially when the whiskers are distributed evenly. But it is rubbish at giving the user an image of the object itself unless they aim at it and look it up and down a little. Magic will also distort whiskers or make them collide when they shouldn't, letting very keen users detect illusions or enchantments more easily. So a choice has to be made between peripheral vision and selective vision.
This is not to be confused with actual Reizosense, which is filed under Blindsight.

Option 4: Wide-band Emissive Darkvision. Your eyes have built in flashlights.
Kobold: Alright, I can see SOMETHING in there, but my Darkvision doesn't reach that far.
Warforged: Not To Worry. I Am ALSO Equipped With Darkvision.
Kobold: Uh. Yeah no, that's just headlights. You have headlights, Dorfl.
Warforged: It Is Communal Darkvision.

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