knitr code chunk options are simply R code, so you can have a code chunk that only runs based on some condition. For example,
---
output: rmarkdown::word_document
---
```{r}
show_image <- TRUE
```
```{r eval=show_image}
# Some plotting code
plot(...)
```
Whether show_image evlauates to TRUE or FALSE will control whether the code chunk is evaluated and the plot is included in the document.