The tentative name for the book is The Filter Trap, which refers to both a combination of the Great Filter theory and it being a trap. This refers to one of the solutions to Fermi's Paradox of why we can't find any intelligent life in the universe.
If a designer wants to do an image of a ship or alien let me know and I can provide descriptions of a few key scenes and what the aliens look like.
Actually: here are a few descriptions and events in the story:
A species of aliens invades the planet via "spike" shaped ships that slam down into a pool of energy absorbing black nanites (that land first). The aliens that emerge are about 3-4 feet tall and are shaped like four legged starfish, but with multi-colored "fur." They can grow tools from the nanite material from the "mitts" at the end of their arms/feet. They have no heads, but instead have multiple dark eyes around the central part of their body, which also has a small opening to breathe/eat. These are the aliens that encase the air force pilot in the desert in the black nanite material. One of the tools they can grow from the nanites is a "laser" which they use as a weapon in battle.
Another species of aliens on a different planet is very tall and thin (15 feet or so), with long limbs and fingers. Their heads are roughly shaped like a deer and have very ornate and intricate antler-like growths extending from several points on the head. Eyes are large and single-colored (but the colors vary from person to person). A scene that stood out to a beta reader was when a "council" of these aliens talked with two human scientists (a man and a woman) in a large ovoid chamber. The aliens floated on unseen chairs and wore robes. The room was underground and had light filtering down through a series of mirrors. Behind the floating aliens was a carved panorama of the aliens' civilization in the stone wall. These aliens can communicate telepathically, so they do not open their mouths.
Another alien species is based on an older evolutionary cousin of the tardigrade. It's gray with elephant-like skin and has multiple stubby arms/hands and dark red eyes at equidistant points along the body. Unlike tardigrades on earth there is no head and no openings on the body. These aliens travel through space in enclosures like a barium chamber and may be present at the birth of suns/worlds/galaxies. In the novel they have the ability to communicate telepathically, and are the oldest characters. They have the ability to manipulate matter via thought, and at one point build a ship in an underground "warehouse" of alien technology to tunnel through the rock overhead and then travel through space. The "ship" is about the size of a saturn V rocket.
One of these tardigrades at one point engages all the humans on the earth in a simulation of floating in space in successive spheres around it, while it answers their questions about the invation/great filter/etc.
Other possibilities are scenes of destruction. Boston, Hawaii, San Francisco and Los Angeles are all nearly demolished by 100+ foot high tsunami waves.
A group of American soldiers at one point has a battle with the "starfish" shaped aliens in the Los Angeles wreckage at one point.
Another battle, an all-out one, takes place with thousands of troops in the Mojave Desert as they launch an assault on one of the miles-long alien ships (black, spikey). The "starfish" like aliens are slicing through American helicopters and jets as they try to drop bombs, etc. Soldiers attempt to lead three scientists through this to get into the ship...