With all respect to everybody else who has supplied cases for the Olimex ESP32-POE on here, I don't like any of them, sorry! So I ended up making my own set of cases:

1. The mini case, this one, measuring 100 mm long, 35 mm wide and 35 mm tall, which contains the board only.
2. The midi case, measuring 100 mm long, 60 mm wide and 35 mm tall, which can additionally take a 2400 mAh battery and an Olimex UEXT breakout board or any similar width (20-25 mm) peripheral.
3. The maxi case, measuring 100 mm long, 140 mm wide, and 35 mm tall, which is the midi case with an additional 75 mm wide thermally separated section for things like temperature sensors or relays. The thermally separated section has printed-in offset mounts for M2.5-M3 board screws. I chose 75 mm as the largest breakout board I have apart from relay clusters is 65 mm.

Each of those has its own Thingiverse item, linked.

All the cases have the same base and can reuse lids etc. Here were my design goals:

1. The Olimex ESP32-POE being a sub €20 PoE device runs hot at about 80 C if idling, and 120 C is expected if you're drawing all four watts it is capable of from ethernet. What I don't like about the other cases is they put plastic right up next to the hot power conversion circuitry near the ethernet port (see thermal photo attached). If that is PLA, it becomes a goopy mess, PETG will lose structural stability, and even ABS may creep. My cases put a full 10 mm ventilated air gap between plastic and hot components, spreading out the heat load, and I use a much thicker base than some other cases.

2. Sometimes you want to drive self tapping screws into the case to hold in place breakout boards and sensors, and for that you need a good thick base. I gave mine a 4mm base with regularly spaced countersunk holes for screws to fix the case onto something.

3. The other cases don't expose every port and connector of the Olimex ESP32-POE for use. Often the battery connector is obstructed, or the USB port, or even the soldered breakout pins at the sides. My cases expose everything the board has in full, unobstructed. I even put in a hole so you can see the ethernet leds.

4. The ethernet port on the ESP32-POE has spring metal around its sides, and I saw few other cases leveraging that. Mine uses those to provide back pressure holding the board's wifi antenna into a slot at the back of the case, thus holding the board firm. It also means to get the board in and out of the case just needs a little push and a pop.

These cases are sized for Rev. L of the Olimex ESP32-POE, so the > 2021 edition with the lower heat PoE circuitry. Even then, resistor R42 burns min 0.5 watts always on PoE, so at idle approx 0.8 watts of heat will be generated. Me personally, I wouldn't risk normal PLA on that, you'd better use a special PLA more stable at high temperatures. PETG starts getting a bit soft after 50 C, but should hold its integrity until 65 C. I did test printing this case in PETG, and it came out lovely. ABS is obviously the best choice if your printer can do it, that should hold its integrity until 80 C. However there is slightly more shrinkage with ABS.

I sized this model for PETG with it being a touch tight with ABS as a result. It's no showstopper, just be prepared to be a little forceful if you printed in ABS. The pictures above are for white ABS, and I can confirm the board can be inserted and removed in an ABS print with only minor hassle. The case thicknesses are a touch overkill for ABS which is much stronger than PETG, but for PETG they are spot on - thin enough you're not wasting material, but no more.

The lid's holes were designed so an Olimex UEXT cable can be put through them without issue. The lid has a good tight fit in the mini case, and I gave it 2 mm thickness so it wouldn't suck if printed in PETG.

I personally think these cases are pretty much perfect, but I look forward to seeing what remixes you all do. Enjoy!