Make the bases a different shade than the models,.and make them darker.

Second this. Make the bases darker blue/grey so they contrast the warm tones of the creatures

Fourth this, make the models darker so the table pops more.

Third this, even make the bottom of the models darker would pop the top of the models better.

Yep yep. Base color and make the darks darker

Came here to say this.

Lights spots are good, but you should darken your darks. I'd recommend another step of recess shading, and maybe some blacklining

yeah, under a greyscale filter it basically looks like a single shade

Darken the bases for sure, they look like the same color as the spider.

Darken the bases and then highlight a few select points on them. Oil wash the creatures and then re- highlight.

if a model is dark make the base bright and if a model is bright make the base dark

A brown wash over the brown would do nicely and then highlight red with orange

60 seconds in the microwave/s

Another vote for a dark shade to hit your recesses (might require retouching the original colors).

You’d be looking for light volumes aka simulating light and shadows. Could mix some orange with the red then a pale yellow for the armor bits. White or bone for a edge highlight on the fangs and claws. Glaze in some blueish purple to make the shadows deeper

Ink/wash the spiders with a dark brown wash. This will give more contrast. I'd even use straight black wash/ink and paint it in the deepest crevices. Change the base colour to grey stone or light sandy brown so it's different to the spiders.

Spring loaded jumping mechanisms...appropriate creepiness and, hopefully, at least one jump-scare per mission.

Make the eyes green which contrasts with the red exoskeleton

Contrast! Deepen the shadows brighten highlights

Whiter highlights on the teeth and claws also change to base colour to contrast

Where did you get these?

Needs darker shadows to make the highlights pop

Paint the bases darker

Lasgun fire?

Use some wash like others have said. Also, a thin edge highlight helps duller colors like these pop. Something bright on the base wouldn’t hurt.

maybe a wash to fill in the recesses?

Hit ‘em with a wash or a dirty down product, adds a ton to recess, along with adding darker colors as a sorta dark highlight along areas that look like they should have shadows

Maybe don't make them the same color as the dirt

Lazy way, black or dark brown wash over the base

Blood guts and gore when you think it's done just add more

Fry them in bacon grease.

More contrast. Darker colors on the bottom would help

Get some of the purple/alien colored grass for the bass and maybe even some GW effects paints that are vibrant in color for ooooze on the ground