Dioniso is totally right 
Player, enemys and hearts are sprites.
they're distributed to avoid more than 4 in a row as much as possible,, even it can happen sometimes.
All is MSX1, but that screenshoot was taken with a MSX2 palette which looks bit better.
Well it was ported to the Spectrum so it should at lest be possible to port on MSX with some improved coloring and use some sprites... Doesnt have to be a pixel perfect arcade port
- Digitized images, there are loads of tools nowadays to convert them to MSX1
- Digitized speech: Just the name of the game, or one scream etc would be nice. 
If digitizing (colourful) pictures for MSX gives just a mess, then just draw wanted life-like pictures using some msx paint program! (thought you need some artistic skills for that)
Probably we all remember that feeling when we heard our msx SPEAKING every now and then in the 1980s! Just remember JET BOMBER and NORTH SEA HELICOPTER!! That´s why I still like to hear some (well planned and well spoken) speech!
MSX games are looking better and better all the time, but there´s still a place for little but important improvements. Think about little animations... how many MSX dev game sprites or backgrounds really act and look like in true life? I mean, heroes and villains have just some animation frames and that´s it. They always have same face, either they always look mean or happy, and that´s it. Maybe some hero may look unhappy when dying, but that´s all... Background is usually still without any animation. Imagine how good your game will look if you just make your hero and villains occasionally waving their hands or just turn their heads to player and talk (imagine little mouth animation here), both villains and heroes could have expressions in their faces, like if you escape villains by jumping to platform where they can´t reach you, their faces could show some angryness. And backgrounds... does backgrounds need to be still all the time? In simplest way, it´s just few more characters more to make tree leaves shake in the wind, and remember, it´s not windy all the time in real life, so why it has to be in your game.
Here´s some little examples:
BOULDERDASH - it was unforgettable moment to see rockford winking his eyes and stomping his feet and waving his hands!
NIGHTSHADE - every now and then hero looks around, to see if there´s monsters around, no matter are you walking or standing, he still keeps looking around, just like real person would do in such situation!
BARBARIAN - not MSX game, but if you do nothing, player starts waving his hand and "talks" just to make you PLAY the game.
PREHISTORIK 2 - not MSX game either (1992 PC game) but when you don´t touch joystick, hero immediately starts Rockin´ (making some filthy pelvis movements) and bushes do the same all the time, it´s very little thing to program it, but it gives game very good look!!!!!
JACK THE NIPPER II - nipper keeps diggin´ his nose every now and then... 
and that simple water animation looks nice!
Maybe your game also could have some little "unneeded" animations, like if there´s water around, some little fish could occasionally lift their heads from water or just jump, they don´t need to be enemies at all, but a non-harmful animation pleasing player´s eye! Or birds could fly to trees and wave their wings and then start to sleep, or whatever.
Just use your IMAGINATION and give your own game that special touch which makes your game stand out from the crowd!!
And yes, PLEASE MAKE GOOD LOOKING "VIEW FROM BEHIND YOUR CAR" RACING GAME FOR MSX!! There´s NOT many for MSX...... and if doing so, please add varying side-of-the-road-background there, as it is VERY BORING just to watch mountains or eiffel tower in the horizon like in Hyper Rally!! And please make different looking cars too!
Don't you forget Charles Bronson in Death Wish III? When no bullets left you get a new animation while you try to shoot!