Hello Loupgar,
Thanks for your input. We do intend to add some real art (characters, rooms, UI, etc.) as we continue to develop. Later this week we'll add an update with some of the room assets.
Regarding money gain, doing missions (and opening the loot crate rewards) and rushing rooms both reward money (room rushing needs a rebalance) and can usually be done fairly quickly. Sending your survivors to explore the wasteland can also reward money, though its a longer-term investment. Selling unneed armor and weapons will net some money as well. Finally, selling slaves to the Trader (a visiting NPC that will sometimes wander your vault) can also earn you money, giving you an incentive to breed and train your slaves, since the Trader's prices will scale with the stat value and genetic traits of your slaves.
As for customization, there is a gameconfig.ini located in your save directory (usually C:\Users\{username}\AppData\LocalLow\Black Orchard Studios\Vaultkeeper) where you can modify various settings. We will release a devlog on this .ini sometime this week explaining all the variables and how they work. Some of these may get integrated into the in-game menu, we're still doing balancing and figuring out what should and shouldn't be adjustable. For now, there are several breeding related variables under the [Population] section that can be adjusted to your liking.
The breeding system was balanced using Fallout Shelter (the game we based this on) as the base. Where in Fallout Shelter the time to get pregnant is usually very short, the time to gestate is 3 hours and the time for the child to grow is 3 hours, giving a little over 6 hours for the whole process of breeding a new unit. In Vaultkeeper, the time to impregnate lowers with the Luster stat of both participants, the size of the breeing room, and the tier of the breeding room. The time to gestate starts at 1 hour and can be reduced with a genetic trait, and the time for the child to grow to adulthood is also 1 hour and can also be lowered with a genetic trait. Overall, the worst case scenario, with Luster at 1, no genetic traits, and the worst breeding room (Tier 1, 1 wide) the total breeding time takes about 3 hours. With relevant genetic traits, the best breeding room, and maximum Luster stats, plus Luster raising outfits, the total breeding time is 54 minutes. Like everything else in Vaultkeeper, training your Survivors and giving them the right equipment for the job will increase their efficiently greatly, and is part of the core gameplay loop.
Thank you for your feedback and we look forward to hearing more from the community about how we can improve the game