Religion is a key theme in this novel and in particular Bronte's attitudes towards evangelicalism, and we have a significant number of examples of this in the text, in particular the Christianity of Brocklehurst, Helen Burns, and of course, St. John Rivers. You will want to consider how their views on religion are presented, and how Jane Eyre responds or reacts to them if you want to develop this theme further.
However, you have picked a big theme, so I will consider Chapter 4, which is where we first meet the Rev. Brocklehurst when he comes to Gateshead to meet Jane and organise her removal to Lowood with Mrs. Reed. Key to this episode is the clash between Jane and Brocklehurst over religion and their differences. It is highly significant that when Jane first enters the room, she looks up and sees:
...a black pillar... a straight, narrow, sable-clad shape standing erest on the rug: the grim face at the top was like a carved mask, placed above the shaft by way of capital.
It is highly significant that the Rev. Brocklehurst is described with the colour black, wheras later, St. John Rivers is described in similar ways but with the colour white - both characters are described as stone, marble or pillars, which reflect their unyielding stance and fixed views. Also, what is interesting in this passage is the way that hypocrisy is suggested with an allusion to Little Red Riding Hood:
What a face he had now that it was almost on a level with mine! what a great nose! and what a mouth! and what large prominent teeth!
Of course, this suggests that Rev. Brocklehurst, like the wolf before him, is not being entirely truthful in his character, and also adds an element of danger - he is a wolf dressed as something less threatening, though it is suggested that Jane as a child appears to be well aware of the threat he represents.
The passage also contains much irony - it is highly significant that Brocklehurst, already having been described as a "black pillar", counsels Jane to pray to have her heart of stone replaced by a heart of flesh. It is he of course who has the heart of stone, and is in need of a heart of flesh. This hypocrisy continues in Rev. Brocklehurst's narration to Mrs. Reed of how his daughter commented on the poverty of the girls:
"My second daughter, Augusta, went with her mama to visit the school, and on her return she exclaimed: 'Oh, dear papa, how quiet and plain all the girls at Lowood look; with their hair combed behind their ears, and their long pinafores, and those little holland pockets outside their frocks - they are almost like poor people's children! and,' said she, ' they looked at my dress and mama's, as if they had never seen a silk gown before!'"
It is highly ironic that the Rev. Brocklehurst, whilst espousing "humility" and "mortification" for his students, does not have the same high ideals when it comes to the rearing of his own children, who remain in silk gowns.
So, in this Chapter, the religion of Rev. Brocklehurst is exposed as hypocritical, uncaring and biased. This should help you examine the religious viewpoints presented by other characters. All the best!