Help with linking images to a product to appear in cart via line item selections - Shopify

Hi guys, Im after someone who can talk me through instructions and provide me with the right codes etc for linking images to the cart page to correspond with my customers customised product choices. I am offering customised dresses, I will do my best to explain below... Within my shopify store, I have a specific image to go with each variation my customers create by choosing custom options from drop down boxes but I have no idea how to link them so they appear in thier cart & confimation email.( In the beginning, I did use the variant drop downs that are provided in the page where you add your product but this caused issues with my inventory as I can only use,for example, the black and yellow fabric once (I only have enough for one dress because my customers like thier dresses to be one of a kind) So my only fix was to add line item drop down boxes (through editing the HTML codes etc) that didnt affect the inventory and all I want to do is link my images to the options the customers select. I think it might be done in the [login to view URL]? I dont know how to do this, so if they choose a particular colour and sleeve length on a dress the corresponding image will show up in the cart etc so they have confidence they will get what they are paying for. I already have the images I need to use uploaded into my shopify admin, just need to know what code? to use and where to put it to achive the above result. I will attach an image of how it currently looks in the cart screen. in the cart this customer has selected the yellow and black dress, size 8 and (A) sleeveless, You will see that the product image is of three dresses with different sleeves but I want this image, in this case, to show just the sleevless dress on its own so the customer knows their selections look like the picture in thier cart. I already have all the images I need to use saved in my shopify, I belive I can link the image URLs somehow? Thank you!!